%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % 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_1_31_00.tex", Document, 18241, 1/31/2000, 22:42:12, ""% % "/document/graphics/curve.bmp", ImportPict, 23486, 6/24/1999, 16:32:04, ""% % "/document/graphics/rdr.bmp", ImportPict, 13262, 6/24/1999, 16:20:50, ""% % "/document/FP028809.wmf", PlotPict, 6816, 1/25/2000, 17:33:32, "" % % "/document/graphics/maroon2.wmf", ImportPict, 4748, 11/10/1998, 13:11:40, ""% % "/document/FP02880A.wmf", PlotPict, 7866, 1/25/2000, 17:31:02, "" % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%% Start /document/lec_1_31_00.tex %%%%%%%%%%%%%%%%%%% %\newtheorem{theorem}{Theorem} %\newtheorem{axiom}[theorem]{Axiom} %\newtheorem{conjecture}[theorem]{Conjecture} %\newtheorem{corollary}[theorem]{Corollary} %\newtheorem{definition}[theorem]{Definition} %\newtheorem{example}[theorem]{Example} %\newtheorem{exercise}[theorem]{Exercise} %\newtheorem{lemma}[theorem]{Lemma} %\newtheorem{proposition}[theorem]{Proposition} %\newtheorem{remark}[theorem]{Remark} \documentclass{article} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \usepackage{graphicx} \usepackage{amsmath} %TCIDATA{OutputFilter=LATEX.DLL} %TCIDATA{Created=Sunday, May 16, 1999 12:00:37} %TCIDATA{LastRevised=Monday, January 31, 2000 17:42:11} %TCIDATA{} %TCIDATA{} %TCIDATA{CSTFile=webmath.cst} %TCIDATA{PageSetup=72,72,72,72,0} %TCIDATA{AllPages= %F=36,\PARA{038

\hfill \thepage} %} \newtheorem{acknowledgement}[theorem]{Acknowledgement} \newtheorem{algorithm}[theorem]{Algorithm} \newtheorem{case}[theorem]{Case} \newtheorem{claim}[theorem]{Claim} \newtheorem{conclusion}[theorem]{Conclusion} \newtheorem{condition}[theorem]{Condition} \newtheorem{criterion}[theorem]{Criterion} \newtheorem{notation}[theorem]{Notation} \newtheorem{problem}[theorem]{Problem} \newtheorem{solution}[theorem]{Solution} \newtheorem{summary}[theorem]{Summary} \newenvironment{proof}[1][Proof]{\textbf{#1.} }{\ \rule{0.5em}{0.5em}} \input{tcilatex} \begin{document} \section{Ma 116 Lecture 1/31/00} \subsection{Vector Functions} SNB uses the convention of writing a vector $v_{1}\vec{i}+v_{2}\vec{j}+v_{3}% \vec{k}$ in the form $\left( v_{1},v_{2},v_{3}\right) .$ We shall use these notations interchangeably. Consider now a particle $P$ moving in $x,y,z-$space along a curve $C.$ \begin{center} \FRAME{dtbpFU}{3.5397in}{2.5944in}{0pt}{\Qcb{Particle Moving Along a Curve }% }{}{curve.bmp}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "USEDEF";valid_file "F";width 3.5397in;height 2.5944in;depth 0pt;original-width 5.2191in;original-height 3.8121in;cropleft "0";croptop "1";cropright "1";cropbottom "0";filename 'graphics/curve.bmp';file-properties "XNPEU";}} \vspace{1pt} \end{center} If $\ \vec{r}$ is the vector from the origin to the point $\left( x\left( t\right) ,y\left( t\right) ,z\left( t\right) \right) $ where the particle is at time $t,$ then \vspace{1pt} \begin{equation*} \vec{r}\left( t\right) =x\left( t\right) \vec{i}+y\left( t\right) \vec{j}% +z\left( t\right) \vec{k} \end{equation*} We say that $\vec{r}\left( t\right) $ is a vector function of $t.$ \vspace{1pt} More generally, if $\vec{V}=\vec{V}\left( t\right) $ is a vector function of $t,$ then \vspace{1pt} \begin{center} \begin{equation*} \vec{V}\left( t\right) =V_{1}\left( t\right) \vec{i}+V_{2}\left( t\right) \vec{j}+V_{3}\left( t\right) \vec{k} \end{equation*} \end{center} \vspace{1pt} We say the $\vec{V}\left( t\right) $ is \emph{continuous} if $V_{1}\left( t\right) ,V_{2}\left( t\right) ,$ and $V_{3}\left( t\right) $ are all continuous. If $V_{1}\left( t\right) ,V_{2}\left( t\right) ,$ and $% V_{3}\left( t\right) $ are all differentiable, then we define the derivative of $\vec{V}$ by \vspace{1pt} \begin{equation*} \dfrac{d\vec{V}}{dt}=\dfrac{dV_{1}}{dt}\vec{i}+\dfrac{dV_{2}}{dt}\vec{j}+% \dfrac{dV_{3}}{dt}\vec{k} \end{equation*} If $V_{1}\left( t\right) ,V_{2}\left( t\right) ,$ and $V_{3}\left( t\right) $ are all integrable, then we define the integral of $\vec{V}$ \ by \vspace{1pt} \begin{equation*} \int \vec{V}\left( t\right) dt=\int V_{1}\left( t\right) \vec{i}+\int V_{2}\left( t\right) \vec{j}+\int V_{3}\left( t\right) \vec{k} \end{equation*} \vspace{1pt} Remark: $\vec{r}\left( t\right) =x\left( t\right) \vec{i}+y\left( t\right) \vec{j}+z\left( t\right) $\vspace{1pt}$\vec{k}$ is called the position vector of a curve $C:x\left( t\right) ,y\left( t\right) ,z\left( t\right) .$ Let us consider $\vec{r}$ at $t$ and at a nearby subsequent point $t+\Delta t.$ \begin{center} \FRAME{dtbpF}{3.8303in}{2.9084in}{0pt}{}{}{rdr.bmp}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "USEDEF";valid_file "F";width 3.8303in;height 2.9084in;depth 0pt;original-width 3.781in;original-height 2.8643in;cropleft "0";croptop "1";cropright "1";cropbottom "0";filename 'graphics/rdr.bmp';file-properties "XNPEU";}} \end{center} \vspace{1pt} Note that $\dfrac{\Delta \vec{r}}{\Delta t}$ has the same direction as $% \Delta \vec{r}$ since $\Delta t>0.$ Thus as $\Delta t\rightarrow 0,$ $\dfrac{% \Delta \vec{r}}{\Delta t}\rightarrow \dfrac{d\vec{r}}{dt}$ and this is the direction of the tangent vector to $C$ at any point $\left( x\left( t\right) ,y\left( t\right) ,z\left( t\right) \right) .$ \begin{example} At what point or points is the tangent to the curve $% C:x=t^{3},y=5t^{2},z=10t $ perpendicular to the direction of the tangent when $t=1.$ \end{example} We graph the curve first. $\left[ \begin{array}{ccc} t^{3} & 5t^{2} & 10t% \end{array}% \right] $\FRAME{dtbpFX}{3in}{2.0003in}{0pt}{}{}{Plot}{\special{language "Scientific Word";type "MAPLEPLOT";width 3in;height 2.0003in;depth 0pt;display "USEDEF";plot_snapshots TRUE;recompute FALSE;lastEngine "Maple";xmin "-5";xmax "5";xviewmin "-130.000000022";xviewmax "130.10000112244";yviewmin "-2.4468971472996";yviewmax "127.548938656946";zviewmin "-52.0000000028";zviewmax "52.040000142856";phi 45;theta 45;plottype 5;num-x-gridlines 25;num-y-gridlines 25;axesstyle "Normal";xis \TEXUX{t};var1name \TEXUX{$t$};var2name \TEXUX{$y$};function \TEXUX{$\left[ \MATRIX{3,1}{c}\VR{,,c,,,}{,,c,,,}{,,c,,,}{,,,,,}\HR{,}\CELL{t^{3}}% \CELL{5t^{2}}\CELL{10t}\right] $};linecolor "Black";linestyle 1;pointstyle "Point";linethickness 3;lineAttributes "Solid";var1range "-5,5";surfaceColor "[linear:XYZ:RGB:0x00ff0000:0x000000ff]";num-x-gridlines 50;valid_file "T";tempfilename 'FP028809.wmf';tempfile-properties "XPR";}} We may represent $C$ by the vector $\vec{r}(t)=t^{3}\vec{i}+5t^{2}\vec{j}+10t% \vec{k}.$ Then the tangent to $C$ at any point is \vspace{1pt} \begin{equation*} \frac{d\vec{r}}{dt}=3t^{2}\vec{i}+10t\vec{j}+10\vec{k} \end{equation*} \vspace{1pt} At $t=1$ the tangent is $\vec{W}=3\vec{i}+10\vec{j}+10\vec{k}.$ To find where $\dfrac{d\vec{r}}{dt}$ is perpendicular to $\vec{W}$ we set the dot product of these vectors equal to $0.$ \vspace{1pt}$\frac{d\vec{r}}{dt}\cdot \vec{W}=\left( 3t^{2},10t,10\right) \cdot \left( 3,10,10\right) =\allowbreak 100+9t^{2}+100t=0$, Solution is: $% \left\{ t=-10\right\} ,\left\{ t=-\frac{10}{9}\right\} .$ Thus at the points $\left( -1000,500,-100\right) $ and $\left( \frac{-1000}{729},\frac{500}{81},% \frac{-100}{9}\right) $ the tangent is perpendicular to its direction at $% \left( 1,5,10\right) .$ \vspace{1pt} If $\vec{U}$ and $\vec{V}$ are two vector functions of $t$ that are both differentiable, then it is not hard to show that \vspace{1pt} \begin{eqnarray*} \dfrac{d}{dt}\left( \vec{U}\cdot \vec{V}\right) &=&\frac{d\vec{U}}{dt}\cdot \vec{V}+\vec{U}\cdot \frac{d\vec{V}}{dt} \\ \frac{d}{dt}\left( \vec{U}\times \vec{V}\right) &=&\frac{d\vec{U}}{dt}\times \vec{V}+\vec{U}\times \frac{d\vec{V}}{dt} \\ \frac{d}{dt}\left[ \vec{U}\cdot \left( \vec{V}\times \vec{W}\right) \right] &=&\frac{d\vec{U}}{dt}\cdot \left( \vec{V}\times \vec{W}\right) +\vec{U}% \cdot \left( \dfrac{d\vec{V}}{dt}\times \vec{W}\right) +\vec{U}\cdot \left( \vec{V}\times \dfrac{d\vec{W}}{dt}\right) \end{eqnarray*} \vspace{1pt} If $\vec{U}=\left( u_{1},u_{2},u_{3}\right) ,\vec{V}=\left( v_{1},v_{2},v_{3}\right) ,$ and $\vec{W}=\left( w_{1},w_{2},w_{3}\right) ,$ then since \vspace{1pt} \begin{equation*} \vec{U}\cdot \left( \vec{V}\times \vec{W}\right) =\left| \begin{array}{ccc} u_{1} & u_{2} & u_{3} \\ v_{1} & v_{2} & v_{3} \\ w_{1} & w_{2} & w_{3}% \end{array}% \right| \end{equation*} \vspace{1pt} the last equation above leads to the following interesting formula for the derivative of a $3\times 3$ determinant. \vspace{1pt} \begin{equation*} \dfrac{d}{dt}\left| \begin{array}{ccc} u_{1} & u_{2} & u_{3} \\ v_{1} & v_{2} & v_{3} \\ w_{1} & w_{2} & w_{3}% \end{array}% \right| =\left| \begin{array}{ccc} \frac{du_{1}}{dt} & \frac{du_{2}}{dt} & \frac{du_{3}}{dt} \\ v_{1} & v_{2} & v_{3} \\ w_{1} & w_{2} & w_{3}% \end{array}% \right| +\left| \begin{array}{ccc} u_{1} & u_{2} & u_{3} \\ \frac{dv_{1}}{dt} & \frac{dv_{2}}{dt} & \frac{dv_{3}}{dt} \\ w_{1} & w_{2} & w_{3}% \end{array}% \right| +\left| \begin{array}{ccc} u_{1} & u_{2} & u_{3} \\ v_{1} & v_{2} & v_{3} \\ \frac{dw_{1}}{dt} & \frac{dw_{2}}{dt} & \frac{dw_{3}}{dt}% \end{array}% \right| \end{equation*} \vspace{1pt} \FRAME{dtbpF}{4.1459in}{0.0735in}{0pt}{}{}{maroon2.wmf}{\special{language "Scientific Word";type "GRAPHIC";maintain-aspect-ratio TRUE;display "PICT";valid_file "F";width 4.1459in;height 0.0735in;depth 0pt;original-width 287.1875pt;original-height 3.1875pt;cropleft "0";croptop "0.053";cropright "1";cropbottom "0.947";filename 'graphics/maroon2.wmf';file-properties "XNPEU";}} \subsection{Arc Length in Three Dimensions} Let $C$ $:\left( x\left( t\right) ,y\left( t\right) ,z\left( t\right) \right) $ $a\leq t\leq b$ be a curve in three space and suppose that $C$ is \emph{smooth.} By this it is meant that $x^{\prime }\left( t\right) ,y^{\prime }\left( t\right) ,$ and $z^{\prime }\left( t\right) $ are continuous and not all simultaneously zero on $a