%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % Scientific Word Wrap/Unwrap Version 2.5 % % Scientific Word Wrap/Unwrap Version 3.0 % % % % If you are separating the files in this message by hand, you will % % need to identify the file type and place it in the appropriate % % directory. The possible types are: Document, DocAssoc, Other, % % Macro, Style, Graphic, PastedPict, and PlotPict. Extract files % % tagged as Document, DocAssoc, or Other into your TeX source file % % directory. Macro files go into your TeX macros directory. Style % % files are used by Scientific Word and do not need to be extracted. % % Graphic, PastedPict, and PlotPict files should be placed in a % % graphics directory. % % % % Graphic files need to be converted from the text format (this is % % done for e-mail compatability) to the original 8-bit binary format. % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % Files included: % % % % "/document/lec_9_15_99.tex", Document, 52018, 9/16/1999, 16:25:38, ""% % "/document/graphics/maroon__3.wmf", ImportPict, 4444, 1/20/1999, 15:54:48, ""% % "/document/graphics/glim11.wmf", ImportPict, 20660, 1/20/1999, 15:54:46, ""% % "/document/graphics/glim14.wmf", ImportPict, 6594, 1/20/1999, 15:54:48, ""% % "/document/FI2DPK04.wmf", PlotPict, 17754, 9/14/1999, 19:19:44, "" % % "/document/graphics/maroon.wmf", ImportPict, 4444, 1/8/1998, 12:13:42, ""% % "/document/graphics/maroon__1.wmf", ImportPict, 4444, 1/8/1998, 12:13:42, ""% % "/document/graphics/maroon__2.wmf", ImportPict, 4444, 2/23/1998, 1:16:50, ""% % "/document/FI1ZZS0L.wmf", PlotPict, 8448, 9/10/1999, 15:14:16, "" % % "/document/FI1ZZS0M.wmf", PlotPict, 8448, 9/10/1999, 15:14:18, "" % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%% Start /document/lec_9_15_99.tex %%%%%%%%%%%%%%%%%%% %% This document created by Scientific Notebook (R) Version 3.0 \documentclass[12pt,thmsa]{article} \usepackage{amssymb} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \usepackage{sw20jart} %TCIDATA{TCIstyle=article/art4.lat,jart,sw20jart} %TCIDATA{OutputFilter=LATEX.DLL} %TCIDATA{Created=Mon Aug 19 14:52:24 1996} %TCIDATA{LastRevised=Thursday, September 16, 1999 12:25:36} %TCIDATA{} %TCIDATA{CSTFile=webmath.cst} %TCIDATA{PageSetup=72,72,72,72,0} %TCIDATA{AllPages= %F=36,\PARA{038
\hfill \thepage} %} \input{tcilatex} \begin{document} \section{\protect\vspace{1pt}Ma 115 Lecture 9/15/99} Before we continue with our discussion of derivatives we will discuss some more aspects of limits involving infinity. \subsection{Horizontal asymptotes} \vspace{1pt} \textsl{Horizontal asymptotes} is the name given to the horizontal lines these functions approach. \begin{definition} The line $y=L$ is called a \emph{horizontal asymptote} of the function $% f\,\left( x\right) $ if either \[ \lim_{x\rightarrow \infty }\,f\,\left( x\right) =L\;\text{or\ }% \lim_{x\rightarrow \left( -\,\,\infty \right) }\,f\,\left( x\right) =L \] \FRAME{dtbpF}{4.1943in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.5002";cropright "1";cropbottom "0.4999";filename 'graphics/maroon__3.wmf';file-properties "XNPEU";}} \end{definition} Some functions can have two different asymptotes like the function show below; \[ \FRAME{itbpFU}{3.5526in}{1.7772in}{0in}{\Qcb{Two asymptotes}}{}{glim11.wmf}{% \special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.5526in;height 1.7772in;depth 0in;original-width 245.875pt;original-height 122pt;cropleft "0";croptop "1";cropright "1";cropbottom "0";filename 'graphics/glim11.wmf';file-properties "XNPEU";}} \] Some functions can have just one asymptote like the function below. \[ \FRAME{itbpFU}{2.968in}{1.2816in}{0in}{\Qcb{One asymptote}}{}{glim14.wmf}{% \special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 2.968in;height 1.2816in;depth 0in;original-width 205pt;original-height 87.4375pt;cropleft "0";croptop "1";cropright "1";cropbottom "0";filename 'graphics/glim14.wmf';file-properties "XNPEU";}} \] \vspace{1pt}\vspace{1pt}\FRAME{dtbpF}{4.1943in}{0.0623in}{0pt}{}{}{maroon.wmf% }{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6905";cropright "1";cropbottom "0.6349";filename 'graphics/maroon__3.wmf';file-properties "XNPEU";}} \FRAME{dtbpF}{4.1943in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.7183";cropright "1";cropbottom "0.6071";filename 'graphics/maroon__3.wmf';file-properties "XNPEU";}} \begin{example} Find the horizontal asymptote(s) for $f\left( x\right) =\dfrac{\sqrt{3x^{2}+1% }}{2x-3}$ \end{example} \emph{Solution}. \ First assume that $x\rightarrow \infty .$ \begin{eqnarray*} \dfrac{\sqrt{3x^{2}+1}}{2x-3} &=&\dfrac{\sqrt{x^{2}\left( 3+\dfrac{1}{x^{2}}% \right) }}{x\left( 2-\dfrac{3}{x}\right) } \\ &=&\dfrac{x\sqrt{\left( 3+\dfrac{1}{x^{2}}\right) }}{x\left( 2-\dfrac{3}{x}% \right) } \\ &=&\dfrac{\sqrt{\left( 3+\dfrac{1}{x^{2}}\right) }}{\left( 2-\dfrac{3}{x}% \right) } \end{eqnarray*}% The limit of the numerator is $\sqrt{3};$ \ the limit of the denominator is $% 2.$ \ Thus \[ \lim_{x\rightarrow \infty }\dfrac{\sqrt{3x^{2}+1}}{2x-3}=\dfrac{\sqrt{3}}{2} \] \QTR{green}{Exercise}. \ We leave it to the reader to show that \[ \lim_{x\rightarrow \,-\,\,\infty }\dfrac{\sqrt{3x^{2}+1}}{2x-3}=\dfrac{-% \sqrt{3}}{2} \]% This example has two horizontal asymptotes, $y=\dfrac{\sqrt{3}}{2}$ and $y=-% \dfrac{\sqrt{3}}{2}.$ \ Here's the graph. (Asyptototes are in green.) \[ \FRAME{itbpF}{3.3001in}{2.2009in}{-0.0069in}{}{}{Plot}{\special{language "Scientific Word";type "MAPLEPLOT";width 3.3001in;height 2.2009in;depth -0.0069in;display "USEDEF";plot_snapshots TRUE;function \TEXUX{$\dfrac{\sqrt{3x^{2}+1}}{2x-3}$};linecolor "Red";linestyle 1;linethickness 2;pointstyle "Point";function \TEXUX{$\MATRIX{2,2}{c}\VR{,,l,,,}{,,l,,,}{,,,,,}\HR{,,}\CELL{3/2}\CELL{20}% \CELL{3/2}\CELL{-20}$};linecolor "Green";linestyle 4;linethickness 1;pointstyle "Point";function \TEXUX{$\dfrac{\sqrt{3}}{2}$};linecolor "Green";linestyle 4;linethickness 1;pointstyle "Point";function \TEXUX{$-\dfrac{\sqrt{3}}{2}$};linecolor "Green";linestyle 4;linethickness 1;pointstyle "Point";xmin "-9";xmax "9";xviewmin "-9";xviewmax "9";yviewmin "-9";yviewmax "8";viewset"XY";rangeset"X";phi 45;theta 45;plottype 4;numpoints 49;axesstyle "normal";xis \TEXUX{x};var1name \TEXUX{$x$};valid_file "T";tempfilename 'FI2DPK04.wmf';tempfile-properties "XPR";}} \] \FRAME{dtbpF}{4.1952in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1952in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.1073";cropright "0.9981";cropbottom "1.2181";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \subsection{ Infinite limits} \vspace{1pt} The expression \[ \lim_{x\rightarrow \infty }f\,\left( x\right) =\infty \] means that the function values become large as $x$ approaches $\infty .$ \vspace{1pt} Normally, we will usually say this means the limit does not exist, but the notation is convenient to describe what is happening to a function as $x$ becomes large. \begin{example} $\lim\limits_{x\rightarrow \,\infty }x^{2}=\infty $ \end{example} \begin{example} Show that $\lim\limits_{x\rightarrow \,\infty }\dfrac{x^{2}+1}{x}=\infty .$ \end{example} \emph{Solution.} \ We rewrite the fraction as \begin{eqnarray*} \dfrac{x^{2}+1}{x} &=&\dfrac{x^{2}(1+\dfrac{1}{x^{2}})}{x} \\ &=&x\left( 1+\dfrac{1}{x^{2}}\right) \end{eqnarray*} The term in parentheses approaches $1,$ while we know that $x$ \ approaches $% \ \infty .$ \ Thus \ \begin{eqnarray*} \lim_{x\rightarrow \infty }\dfrac{x^{2}+1}{x} &=&\infty . \\ && \end{eqnarray*} \begin{example} Find $\lim\limits_{x\rightarrow \infty }\,x^{2}-4x.$ \end{example} \emph{Solution.} \ We first note that we just can't let $x\rightarrow \infty $ for the individual terms and then compute the difference. Why? Because this would result in the expression $\infty -\infty $, which is meaninless. \ But we can algebraically manipulate the expression as \[ x^{2}-4x=x^{2}\left( 1-\dfrac{4}{x}\right) \] Now, we know that $\lim\limits_{x\rightarrow \infty }\left( 1-\dfrac{4}{x}% \right) =1.$ \ It is now easy to see that \[ \lim_{x\rightarrow \infty }\,x^{2}\left( 1-\dfrac{4}{x}\right) =\infty \] \FRAME{dtbpF}{4.1952in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1952in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.1073";cropright "0.9981";cropbottom "1.2181";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \section{Formulas for Derivatives} \vspace{1pt} \subsection{Introduction} \vspace{1pt} {\Large The few formulas we have} don't go very far for finding the derivative of any but the simplest functions. For example, they are of no help in finding the derivative of the function \[ f(x)=(\sqrt{x}+3x^{4})^{10} \] If we were to apply the secant method of the last section for finding its derivative, we would quickly find ourselves in a hopeless morass of algebra. As is often the case in mathematics and other subjects, too, it is imperative to begin with basics. The first basic rule is called the \emph{% Power Rule\/}. \medskip \vspace{1pt}\FRAME{dtbpF}{4.1952in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1952in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6905";cropright "0.9981";cropbottom "0.6349";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \vspace{1pt} The \emph{power rule}, though very important, works best in conjunction with several other rules. \ But first things first. \begin{center} \vspace{1pt}\FRAME{dtbpF}{4.1943in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6968";cropright "1";cropbottom "0.6965";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \subsection{The {\protect\Large Power Rule~}~} \vspace{1pt} \begin{quotation} \textbf{The Power Rule}. For any constant $r$, the derivative of $f(x)=x^{r}$ \ is \[ f\,^{\prime }(x)=rx^{r-1} \] \end{quotation} \vspace{0in}In words, \emph{the derivative of }$x$\emph{\ to a power is the power times }$x$\emph{\ to the power reduced by }$1$\emph{.} \FRAME{dtbpF}{4.0707in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.0707in;height 0.0761in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "1.1665";cropright "1";cropbottom "0.3887";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{example} Find the derivative of $f(x)=x^{3}$. \end{example} \noindent \emph{Solution}~~By the Power Rule, \[ f\,^{\prime }(x)=3x^{3-1}=3x^{2} \] \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6706";cropright "1";cropbottom "0.6703";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{example} Find the derivative of $f(x)=\sqrt{x}$. \end{example} \noindent \emph{Solution}~~Recall that $\sqrt{x}=x^{1/2}$. \ \ Then the Power Rule, with $r=\frac{1}{2}$, is applicable: \[ f\,^{\prime }(x)=\frac{1}{2}x^{(1/2)-1}=\frac{1}{2}x^{-1/2}=\frac{1}{2\sqrt{x% }},\qquad x>0 \] \emph{Note:} \ Recall that the domain of \ $\sqrt{x}$ \ is \thinspace $% \lbrack 0,\infty )$ including $\ x=0$. \ However, the domain of the derivative is only $(0,\infty ),$ \ because its value at \ $\ x=0$ \ is undefined. \vspace{1pt} \FRAME{dtbpF}{4.1943in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9405";cropright "1";cropbottom "0.3849";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} The power rule, though very important, works best in conjunction with several other rules discussed on the next pages. \begin{center} \FRAME{dtbpF}{4.1943in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0761in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9418";cropright "1";cropbottom "0.6084";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \emph{What is remarkable about the power rule is that it is valid for all real numbers }$r.$ {} The proof of the Power Rule is not difficult for positive integers. For fractional powers it is trickier. \ Here we give the proof for a couple of specific cases. In fact for the function $f(x)=x^{2}$, the derivative $% f\;^{\prime }(x)=2x$ \ has already been computed. \begin{center} {} \end{center} \FRAME{dtbpF}{3.2923in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.2923in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6338";cropright "1";cropbottom "0.6335";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \subsection{The {\protect\Large Constant-Multiplier Rule~}~} \vspace{1pt} \begin{quotation} \textbf{Constant-Multiplier Rule.}{\Large ~}For any constant $k$, the derivative of $f(x)=kg(x)$ \ is \[ f^{\,\,\prime }(x)=kg^{\prime }(x) \] \end{quotation} In words, \emph{the derivative of a constant times a function is the constant times the derivative of the function\/}. \vspace{1pt}% \CustomNote[\underline{Proof}]{Margin Hint}{$f^{\,\,\prime }\left( x\right) =% \dfrac{d}{dx}\left( kg\left( x\right) \right) $% \par $=\lim\limits_{h\rightarrow 0}\dfrac{kg\left( x+h\right) -kg\left( x\right) }{h}$% \par $=k\lim\limits_{h\rightarrow 0}\dfrac{g\left( x+h\right) -g\left( x\right) }{% h}$% \par $=kg^{\prime }\left( x\right) $} $\ \ f^{\,\,\prime }\left( x\right) =\dfrac{% d}{dx}\left( kg\left( x\right) \right) $ $=\lim\limits_{h\rightarrow 0}\dfrac{kg\left( x+h\right) -kg\left( x\right) }{h}$ $=k\lim\limits_{h\rightarrow 0}\dfrac{g\left( x+h\right) -g\left( x\right) }{% h}$ $=kg^{\prime }\left( x\right) $ \begin{center} {\Large \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.7664";cropright "1";cropbottom "0.4375";filename 'graphics/maroon.wmf';file-properties "XNPEU";}}} \end{center} We first modify the previous examples and add two new ones. \begin{example} Find the derivative of $f(x)=12x^{3}$. \end{example} \noindent \emph{Solution}~~By the Constant-Multiplier Rule and the Power Rule, \[ f^{\prime }(x)=12\cdot 3x^{3-1}=36x^{2} \] \begin{example} Find the derivative of $f(x)=3\sqrt{x}$. \end{example} \noindent \emph{Solution}~~Recall that $\sqrt{x}=x^{1/2}$. \ \ Recall also that the domain of \ $\sqrt{x}$ \ is \thinspace $\lbrack 0,\infty )$. \ By the Constant-Multiplier Rule and the Power Rule, with $r=\frac{1}{2}$, we have \[ f^{\prime }(x)=3\cdot \frac{1}{2}x^{(1/2)-1}=\frac{3}{2}x^{-1/2}=\frac{3}{2% \sqrt{x}},\qquad x>0 \] Note here that the domain of the derivative is $(0,\infty ),$ \ because its value at \ $\ x=0$ \ is undefined. \begin{example} \vspace{1pt}Differentiate $f(x)=\dfrac{4}{x^{3}}$. \end{example} \noindent \emph{Solution}~~Recall that $\dfrac{4}{x^{3}}=4x^{-3}$. So the Constant-Multiplier Rule, together with the Power Rule, gives \[ f^{\prime }(x)=4(-3x^{-3-1})=-12x^{-4} \] \begin{example} (This example combines the Power Rule with the Constant-Multiplier Rule in general.) If $c$ and $p$ are two fixed constants, differentiate $f(x)=cx^{p}$% . \end{example} \noindent \emph{Solution}~~The Constant-Multiplier Rule and the Power Rule apply to give \[ f^{\prime }(x)=c(px^{p-1})=cpx^{p-1}\ \] \begin{exercise} If $f(t)=4t^{5},$ \ what is $f^{\,\,\prime }(t)$? \end{exercise} $f^{\,\,\prime }(t)=\allowbreak 20t^{4}$ Note the independent variable is \ $t.$ \begin{exercise} If $f(x)=-5x^{-1/3},$ \ what is $f^{\,\,\prime }(t)$? \end{exercise} $f^{\,\,\prime }(t)=\left( -\dfrac{1}{3}\right) \allowbreak (-5)x^{-1/3-1}$ $=\dfrac{5}{3}x^{-4/3}=\dfrac{5}{3\left( \sqrt[3]{x}\right) ^{4}}$ \begin{center} \FRAME{dtbpF}{4.1943in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9405";cropright "1";cropbottom "0.3849";filename 'graphics/maroon__1.wmf';file-properties "XNPEU";}} \vspace{0in} \end{center} \subsection{The Sum Rule} \vspace{1pt} The list of functions we \emph{can\/} differentiate is growing, but it is not yet large enough to tackle the problem posed \ at the beginning of this section (which is to find the derivative of $(\sqrt{x}+3x^{4})^{10}$ ). \ We will at least need to know how to differentiate the sum $\sqrt{x}+3x^{4}$. Differentiating the sum of two functions, each of which we can differentiate, is the content of the \emph{Sum Rule\/}.\medskip \vspace{1pt} \begin{quotation} S\textbf{um Rule}. \ \ \ \ If $f(x)=g(x)+h(x)$, \ then $f\;^{\prime }(x$~$% )=g\,^{\prime }(x)+h^{\prime }(x)$. \medskip \qquad \qquad \qquad If $f(x)=g(x)-h(x)$, \ then $f\;^{\prime }(x$~$% )=g\,^{\prime }(x)-h^{\prime }(x)$. \medskip \end{quotation} In words, \emph{the derivative of a sum is the sum of the derivatives; the derivative of a difference is the difference of the derivatives\/}. \begin{theorem} If $f(x)=g(x)\pm h(x)$, \ then $f\,^{\prime }(x$~$)=g\,^{\prime }(x)\pm h^{\prime }(x)$. \medskip \end{theorem} where the \ $\pm $ \ means ``plus'' or ``minus'', and the same sign is used in both occurances. \begin{center} \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9452";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{example} Differentiate $f(x)=\sqrt{x}+3x^{4},\qquad x>0$. \end{example} \emph{Solution}~~Let $g(x)=\sqrt{x}=x^{1/2}$ and $h(x)=3x^{4}$. From the Power Rule, $g\,^{\prime }(x)=\frac{1}{2}x^{-1/2}$. From the Constant-Multiple Rule and the Power Rule, $h^{\prime }(x)=3(4x^{4-1})=12x^{3}$. So, by the Sum Rule, \[ f\;^{\prime }(x)=\frac{1}{2}x^{-1/2}+12x^{3},\qquad x>0\ \] \begin{center} \vspace{1pt} {\Large \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.5099";cropright "1";cropbottom "0.5096";filename 'graphics/maroon.wmf';file-properties "XNPEU";}}} \end{center} \begin{example} Differentiate $f(x)=x+x^{2}+x^{3}$. \end{example} \emph{Solution}~~The Sum Rule above is for two functions. To differentiate the sum of three functions, apply the Sum Rule twice! That is, let $g(x)=x$ and $h(x)=x^{2}+x^{3}$. Then $f(x)=g(x)+h(x)$. From the Power Rule, $% g\,^{\prime }(x)=1\cdot x^{1-1}=1\cdot x^{0}=1$, and, from the Sum Rule and the Power Rule, $h^{\prime }(x)=2x^{2-1}+3x^{3-1}=2x+3x^{2}$. So \[ f\;^{\prime }(x)=1+2x+3x^{2} \] \vspace{1pt} \FRAME{dtbpF}{4.203in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.203in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9967";cropright "1";cropbottom "0.3966";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{remark} In general, the derivative of the sum of three functions is the sum of the derivatives of these functions. \textbf{Question}: \ What is the derivative of the sum of \emph{any\/} (finite) number of functions? \end{remark} The answer to the question: \ \textbf{What is the derivative of the sum of any finite number of differentiable function }is contained in the following theorem. {} \begin{theorem} Let $f(x)=\sum\limits_{k-1}^{n}\;f_{k}(x).$ Then the derivative of $f(x)$ \ is $f\;^{\prime }(x)=\sum\limits_{k-1}^{n}\;f_{k}^{\;\;\prime }(x)$. \end{theorem} In words, \emph{the derivative of the sum of any finite number of differentiable function is the sum of their derivatives.} {} \FRAME{dtbpF}{3.1176in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";display "PICT";valid_file "F";width 3.1176in;height 0.0623in;depth 0pt;original-width 0pt;original-height 0pt;cropleft "0";croptop "0.671";cropright "1";cropbottom "0.6699";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{example} \vspace{1pt}Differentiate $f(x)=(x^{2}-1)^{2}$. \end{example} \emph{Solution}~~As this function is written, it cannot be differentiated by the rules given so far. However, by expanding the function to \[ f(x)=x^{4}-2x^{2}+1 \] we can easily compute the derivative using the Power, Constant-Multiplier, and Sum Rules. Thus \[ f\;^{\prime }(x)=4x^{3}-4x \] Note that the derivative of $1=x^{0}$ is $0$. \FRAME{dtbpF}{4.203in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.203in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.8301";cropright "1";cropbottom "0.5632";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{example} If $f(t)=4t^{5}-\dfrac{1}{t},$ \ what is $f\;^{\prime }(t)$? \qquad \qquad\ \ \ \end{example} $f\;^{\prime }(t)=20t^{5-1}\allowbreak -(-1)t^{-2}=20t^{4}+\dfrac{1}{t^{2}}=% \dfrac{20t^{6}+1}{t^{2}}$ Note the independent variable is \ $t.$ \begin{example} If $f(x)=-12x^{3}-\dfrac{1}{3}x^{2},$ \ what is $f\;^{\prime }(x)$? \ \qquad \end{example} $f\;^{\prime }(x)=\allowbreak -36x^{2}-\frac{2}{3}x$ \begin{center} \vspace{1pt} {\Large \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.5099";cropright "1";cropbottom "0.5096";filename 'graphics/maroon.wmf';file-properties "XNPEU";}}} \end{center} \vspace{1pt} \emph{Note:} \ The sum rule, the constant-multiplier rule and the power rule allow us to differentiate \emph{any polynomial}. \vspace{1pt}\vspace{0in} \subsection{The Extended Power Rule} \vspace{1pt}{\Large H}ere's a simple function: \ $f(x)=(\sqrt[3]{x}+1)^{6}.$ \ Find $f^{\,\,\prime }(x)$. \ So far, we have no rule to handle this \emph{% power-of-a-function} problem directly. \ We could expand it out and differentiate each summand. Thus \begin{eqnarray*} \frac{d}{dx}(\sqrt[3]{x}+1)^{6} &=&\frac{d}{dx}(\allowbreak x^{2}+6\left( \sqrt[3]{x}\right) ^{5}+15\left( \sqrt[3]{x}\right) ^{4}+20x+15\left( \sqrt[3% ]{x}\right) ^{2}+6\sqrt[3]{x}+1) \\ &=&\allowbreak 2\frac{\left( \sqrt[3]{x}\right) ^{5}+5\left( \sqrt[3]{x}% \right) ^{4}+10x+10\left( \sqrt[3]{x}\right) ^{2}+5\sqrt[3]{x}+1}{\left( \sqrt[3]{x}\right) ^{2}} \end{eqnarray*} There has to be a better way!! \ \ \ And there is............................. It's called the \QTR{blue}{Extended Power Rule. }Sometimes this rule is called the\ \QTR{blue}{Generalized Power Rule. } \noindent \vspace{1pt} \begin{quotation} \textbf{Extended Power Rule. \ \ }\vspace{1pt}If $f(x)=(g(x))^{r}$, \ then $% f\,^{\prime }(x$~$)=r(g(x))^{r-1}g^{\prime }(x)$. \medskip \end{quotation} \noindent \noindent {\Large T}hat is, the \textsl{derivative of a power of a function is the power times the function raised to the power reduced by one and that times the derivative of the function.} \begin{center} \ \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9452";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{remark} Before we consider any examples, there is a matter of \textsl{notation}. The function $[g(x)]^{2}=g(x)\cdot g(x)$, as we know. There is a commonplace alternative way of writing this---namely, $g^{2}(x)=g(x)\cdot g(x)$. So $% [g(x)]^{2}=g^{2}(x)$. In general, for any $r\neq -1$, $[g(x)]^{r}$ and $% g^{r}(x)$ (and even $\left( g(x)\right) ^{r}$) \ mean \emph{exactly\/} the same thing, the $r^{\text{th}}$ power of the function \ $g(x)$. \ \ (The notation $g^{-1}(x)$ has a completely different meaning. It is called the \textsl{inverse} of $g(x)$.\ If $r=-1$ we \emph{must} use the power notation as $[g(x)]^{-1}$ or alternatively $\dfrac{1}{g(x)}$. \end{remark} \begin{center} \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.723";cropright "1";cropbottom "0.6179";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} {\Large W}ith this in mind the Extended Power Rule has the more familiar form\medskip \begin{quotation} \QTR{blue}{Extended Power Rule}\textbf{.} \ If $f(x)=g^{r}(x)$, \ then $% f^{\prime }(x$~$)=rg^{r-1}(x)g^{\prime }(x)$. \medskip \end{quotation} \vspace{1pt} \begin{center} \FRAME{dtbpF}{3.7775in}{0.1055in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";display "PICT";valid_file "F";width 3.7775in;height 0.1055in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6719";cropright "1";cropbottom "0.669";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{example} Differentiate $f(x)=(\sqrt[3]{x}+1)^{6}$. \end{example} \emph{Solution\qquad }With $g(x)=\sqrt[3]{x}+1=x^{\frac{1}{3}}+1$, \ we have by the Power Sum Rules that $\ g^{\prime }(x)=\frac{1}{3}x^{-\frac{2}{3}}$. \ Now apply the Extended Power Rule to obtain \[ f^{\,\,\prime }(x)=6(\sqrt[3]{x}+1)^{6-1}\cdot \frac{1}{3}x^{-\frac{2}{3}}=2% \frac{\left( \sqrt[3]{x}+1\right) ^{5}}{\left( \sqrt[3]{x}\right) ^{2}} \] The simplification step is purely algebraic. \FRAME{dtbpF}{3.7775in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0761in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "1.1650";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \begin{example} Differentiate $f(x)=(x+x^{2})^{3}$. \end{example} \noindent \emph{Solution}~~With $g(x)=x+x^{2}$, we have $f(x)=g^{3}(x)$. Noting that $g^{\prime }(x)=1+2x$ (by the Sum and Power Rules), we can apply the Extended Power Rule to obtain \begin{eqnarray*} f^{\,\,\prime }(x) &=&3(x+x^{2})^{3-1}(1+2x) \\ &=&3(1+2x)(x+x^{2})^{2} \end{eqnarray*} $\hfill $ \begin{center} \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9452";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{example} Differentiate $f(x)=\sqrt{1-x^{2}}$. \end{example} \noindent \emph{Solution}~~Note that $f(x)=(1-x^{2})^{1/2}$. So, with $% g(x)=1-x^{2}$, $f(x)=\lbrack g(x)\rbrack ^{1/2}$. Using the Power and Sum Rules we have $g^{\prime }(x)=0-2x=-2x$ ; thus, \begin{eqnarray*} f^{\prime }(x) &=&\frac{1}{2}(1-x^{2})^{(1/2)-1}\cdot (-2x) \\ &=&-x(1-x^{2})^{-1/2} \end{eqnarray*} or \[ f^{\prime }(x)=\frac{-x}{\sqrt{1-x^{2}}} \] \begin{center} \ $\ \FRAME{itbpF}{3.7775in}{0.0623in}{0in}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0in;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9452";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}}$ \end{center} \begin{itemize} \item \textbf{The extended power rule is one of the most useful rules.} \end{itemize} $\ $ \vspace{1pt}\fbox{Key Words: \ power rule, constant-multiplier rule, extended power rule} \subsubsection{\protect\vspace{1pt}Summary of Known Rules} \begin{quotation} \textbf{Constant Multiplier Rule} \[ \dfrac{d}{dx}\left( cf\,\left( x\right) \right) =cf\,^{\prime }\left( x\right) \] \textbf{Sum Rule} \[ \frac{d}{dx}\lbrack f(x)\pm g(x)\rbrack =f\,^{\prime }(x)\pm g\,^{\prime }(x) \] \textbf{Power Rule} \[ \frac{d}{dx}(x^{r})=rx^{r-1},\quad r\neq 0 \] \end{quotation} \vspace{1pt} \begin{center} \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6706";cropright "1";cropbottom "0.6703";filename 'graphics/maroon.wmf';file-properties "XNPEU";}}\vspace{1pt} \end{center} \subsection{The {\protect\Large Power Rule~}~---\ Example 1} \vspace{1pt}{\Large The most important} examples of the extended power rule come as genuine applications to real world situations. \begin{center} \FRAME{dtbpF}{3.7775in}{0.1185in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.1185in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "1.8133";cropright "1";cropbottom "0.3957";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{example} The cost of manufacture of a (square) notebook computer screen depends on its width $x$ according to the formula \[ C(x)=(2.7x+8.5)^{2.5} \] At what rate is the cost increasing when the screen width is 10 inches? \end{example} \emph{Solution. \ }Since the question asks for a rate of change, we first need to find $C^{\prime }(x).$ \ Apply the \CustomNote[Extended Power Rule]{Margin Hint}{% If\ $f(x)=(g(x))^{r}$, \ then $f^{\,\,\prime }(x$~$)=r(g(x))^{r-1}g^{\prime }(x)$.}\ to get \[ C^{\prime }(x)=2.5(2.7x+8.5)^{1.5}(2.7)\allowbreak \]% $\allowbreak $ Now evaluate \ $C^{\prime }(x)$ \ at \ $x=1$ \ to get \[ C^{\prime }(10)=\allowbreak 1427.\,\allowbreak 73 \] This is interpreted to mean that the cost of increasing the screen width by just one inch, from 10 inches to 11 inches, \ is about \$1427. \begin{remark} $\ $\vspace{1pt}Sometimes $C^{\prime }(x)$ is called the \textsl{marginal cost at }$x$, \ which is a term inherited from the business world which typically means the cost of adding one more unit of the commodity. \ We will see later that the derivative at a point is a better way to define the marginal cost. \end{remark} \begin{center} \FRAME{dtbpF}{4.1943in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.6968";cropright "1";cropbottom "0.6965";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \vspace{1pt} \FRAME{dtbpF}{3.7775in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0761in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.7805";cropright "1";cropbottom "0.7802";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \subsection{The Reciprocal Rule} $\vspace{0in}$ The special case of the Extended Power Rule in which $r=-1$ occurs so frequently, it has its own name. \ It is \vspace{0in} \begin{quotation} \textbf{Reciprocal Rule. \ \ }\vspace{1pt}If $f(x)=(g(x))^{-1}=\dfrac{1}{% g\left( x\right) }$, \ then $f\,^{\,\prime }(x$~$)=-(g(x))^{-2}g\,^{\prime }(x)=\dfrac{-g\,^{\prime }\left( x\right) }{g\left( x\right) ^{2}}$. \medskip \end{quotation} \vspace{0in} In words, \emph{the derivative of the reciprocal of a function is the negative of the derivative of the function divided by the square of the function.} \begin{center} \FRAME{dtbpF}{4.1943in}{0.0692in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1943in;height 0.0692in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9967";cropright "1";cropbottom "0.3966";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \end{center} \begin{example} Differentiate $f(x)=\dfrac{1}{3x^{2}-2x+5}$. \end{example} \emph{Solution}~~With $g(x)=3x^{2}-2x+5$, we have $g\,^{\prime }(x)=6x-2$ (by the Sum, Constant Multiple and Power Rules). \ So, we obtain \[ f\,^{\prime }(x)=\dfrac{-\left( 6x-2\right) }{\left( 3x^{2}-2x+5\right) ^{2}} \] \FRAME{dtbpF}{3.7775in}{0.0623in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 3.7775in;height 0.0623in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.5559";cropright "1";cropbottom "0.5556";filename 'graphics/maroon.wmf';file-properties "XNPEU";}} \vspace{0in}Exponential Functions \begin{center} \vspace{1pt} \end{center} \subsection{\protect\vspace{1pt}Properties of the Exponential Functions} \vspace{1pt} The exponential functions have a number of useful algebraic properties: \begin{quotation} \textbf{Laws of Exponents}~~~For $a>0$:\newline E0~~$a^{0}=1$,\newline E1~~$a^{x+z}=a^{x}a^{z}$,\newline E2~~$a^{x-z}=\dfrac{a^{x}}{a^{z}}$, E3~~$(a^{x})^{z}=a^{xz}$, \qquad \hyperref{\qquad \qquad\ \ \ \ }{}{}{% .\x.21.01.01.tex#prob33}.\newline E4~~$a^{x}b^{x}=(ab)^{x}$,\qquad $b>0$\newline E5~$\dfrac{a^{x}}{b^{x}}=\left( \dfrac{a}{b}\right) ^{x}$,$\qquad b>0$ \end{quotation} \subsubsection{\noindent} \paragraph{Examples} \begin{itemize} \item $2^{4}2^{6}=2^{4+6}=2^{10}=1024$ \item \noindent $3^{8}/3^{6}=3^{8-6}=3^{2}=9$ \item \noindent $(2^{2})^{3}=2^{6}=64$ \item \noindent $(4^{2})^{-2}=4^{-4}=1/256$ \item \noindent $2^{-4}2^{8}=2^{-4+8}=2^{4}=16$ \item \noindent $3^{-2}4^{-2}=12^{-2}=1/12^{2}=1/144$ \end{itemize} $\vspace{1pt}$ $\ \hfill $ \begin{center} \FRAME{dtbpF}{4.2384in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.2384in;height 0.0761in;depth 0pt;original-width 290.5625pt;original-height 1pt;cropleft "0";croptop "0.9608";cropright "1";cropbottom "0.4223";filename 'graphics/maroon__2.wmf';file-properties "XNPEU";}} \vspace{0in}Graphing Exponential Functions \end{center} We use the usual method of plotting points of the function and connecting the dots. \begin{example} Graph $y=2^{x}$ \end{example} \begin{center} \begin{tabular}{|cc|cc|cc|} \hline $x$ & $2^{x}$ & $x$ & $2^{x}$ & $x$ & $2^{x}$ \\ \hline 0 & 1.00 & $\frac{9}{8}$ & 2.18 & $-2$ & 0.25 \\ $\frac{1}{8}$ & 1.09 & $\frac{10}{8}$ & 2.38 & $-1$ & 0.50 \\ $\frac{2}{8}$ & 1.19 & $\frac{11}{8}$ & 2.59 & $-\frac{1}{2}$ & 0.71 \\ $\frac{3}{8}$ & 1.30 & $\frac{12}{8}$ & 2.83 & & \\ $\frac{4}{8}$ & 1.41 & $\frac{13}{8}$ & 3.08 & & \\ $\frac{5}{8}$ & 1.54 & $\frac{14}{8}$ & 3.36 & & \\ $\frac{6}{8}$ & 1.68 & $\frac{15}{8}$ & 3.67 & & \\ $\frac{7}{8}$ & 1.83 & 2 & 4.00 & & \\ 1 & 2.00 & & & & \\ \hline \end{tabular} \bigskip \qquad \FRAME{itbpFU}{3in}{2.0003in}{0.793in}{\Qcb{$y=2^{x}$}}{}{}{% \special{language "Scientific Word";type "MAPLEPLOT";width 3in;height 2.0003in;depth 0.793in;display "USEDEF";function \TEXUX{$\lbrack -2,0.25,-1,0.5,-1/2,0.71\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 0,1,1/8,1.09,2/8,1.19\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 3/8,1.3,4/8,1.41,5/8,1.54\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 6/8,1.68,7/8,1.83,1,2\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 9/8,2.18,10/8,2.38,11/8,2.59\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 12/8,2.83,13/8,3.08,14/8,3.36\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$\lbrack 15/8,3.67,2,4\rbrack $};linecolor "black";linestyle 1;linethickness 1;pointstyle "diamond";pointplot TRUE;function \TEXUX{$2^{x}$};linecolor "red";linestyle 1;linethickness 1;pointstyle "point";xmin "-5";xmax "5";xviewmin "-2";xviewmax "3";yviewmin "0";yviewmax "5";viewset"XY";rangeset"X";phi 45;theta 45;plottype 4;numpoints 49;axesstyle "normal";xis \TEXUX{x};var1name \TEXUX{$x$};}} \end{center} \noindent \FRAME{dtbpF}{5.2096in}{0.0761in}{0pt}{}{}{maroon.wmf}{\special% {language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 5.2096in;height 0.0761in;depth 0pt;original-width 361.375pt;original-height 0.625pt;cropleft "0";croptop "0.9128";cropright "1";cropbottom "0.6399";filename 'graphics/maroon__2.wmf';file-properties "XNPEU";}} The graphs of $y=a^{x}$ for all numbers $a>1$ look much like the graph of $% y=2^{x}$. However, if $01$ and for $00$, it is only necessary to plot a few points and connect them smoothly, using the information that the general shape is as shown below. We note that, for $y=a^{x}$, $a>1$, the graph has the $x$-axis for a horizontal asymptote as $x$ becomes arbitrarily small. A similar observation can be made for $01$ and for $00$, it is only necessary to plot a few points and connect them smoothly, using the information that the general shape is as shown below. We note that, for $y=a^{x}$, $a>1$, the graph has the $x$-axis for a horizontal asymptote as $x$ becomes arbitrarily small. A similar observation can be made for $0