University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 10 - Section 10.1 - Parametrizations of Plane Curves - Exercises - Page 563: 25

Answer

$\left\{\begin{array}{l} x=2+t\\ y=\dfrac{4}{3}t+3 \end{array}\right.\qquad t \leq 0$

Work Step by Step

A point-slope equation of a line passing through (a,b) is $y-b=m(x-a)$. In this problem, $(a,b)=(2,3)$ and $m=\displaystyle \frac{-1-3}{-1-2}=\frac{4}{3}$ We can define the parameter $t$ so that $t=x-a$, so a set of parametric equations is $\left\{\begin{array}{l} x=a+t\\ y=mt+b \end{array}\right.$ so this line can be parametrized with $\left\{\begin{array}{l} x=2+t\\ y=\frac{4}{3}t+3 \end{array}\right.$ We don't want the whole line, just the ray. $(2,3)$ is on the line for $t=0,$ $(-1,-1)$ is on the line for $t=-3,$ (negative t) So the ray can be parametrized with: $\left\{\begin{array}{l} x=2+t\\ y=\frac{4}{3}t+3 \end{array}\right.\qquad t \leq 0$
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