\documentclass[12pt]{article} \author{William Conley} \title{Math 32A - Midterm 1} \date{Sunday, 16 November, 2003} \usepackage{amsfonts} \usepackage{amsmath} \begin{document} \pagestyle{myheadings} \markright{Math 32A - Midterm 1} \begin{enumerate} \item (10 points) Suppose that a swan (not a duck!!) is swimming in the circle described by the path $$ \vec{c}(t) = (cos t, sin t) \qquad t\in\mathbb{R}^+ $$ and that the water temperature is given by $$ T(x,y) = x^2e^y \qquad x,y\in\mathbb{R}. $$ \begin{enumerate} \item Find $DT(x,y)$ and explain what this represents. \item Find $D(T\circ c)(t)$ and explain what this represents. \end{enumerate} \item (10 points) Determine whether the following statements are true or false. If a statement is true, indicate how you could show it. If a statement is false, provide a counterexample. \begin{enumerate} \item If $f(x,y,z) = x^4 + xy + z^3$ then $\nabla f(1,0,1)$ is perpendicular to the surface $f=2$ at the point $(1,0,1)$. \vspace{1ex} This statement is (circle one): \hspace{1.5cm} True \hspace{1.5cm} False \\ Explanation or counterexample: \vspace{1cm} \item If $f(x,y) = ln y$ then $\nabla f(x,y) = \frac{1}{y}$. \vspace{1ex} This statement is (circle one): \hspace{1.5cm} True \hspace{1.5cm} False \\ Explanation or counterexample: \vspace{1cm} \end{enumerate} \item (10 points) Find the absolute maxima and minima of the function $$ f(x,y) = 5x^2 - 2y^2 + 2 $$ on the disk $x^2 + y^2 \le 1$ \item (10 points) Pictured are a contour map of f and a (dashed) curve with equation $g(x,y) = 8$. Estimate the maximum and minimum values of f subject to the constraint $g(x,y) = 8$. Explain your choices. \end{enumerate} \end{document}