Calculus 8th Edition

Published by Cengage
ISBN 10: 1285740629
ISBN 13: 978-1-28574-062-1

Chapter 13 - Vector Functions - Review - Exercises - Page 922: 10

Answer

$r(s)=(\dfrac{s}{\sqrt 3}+1) \lt 1, \sin (\ln (\dfrac{s}{\sqrt 3}+1)), \cos (\ln (\dfrac{s}{\sqrt 3}+1)) \gt$

Work Step by Step

$r(t)=\lt e^t , e^t \sin t, e^t \cos t \gt =e^t\lt 1, \sin t, \cos t\gt $ and $|r'(t)=e^t\lt 1, \cos t+\sin t, \cos t-\sin t\gt $ Further, $|r'(t)|^2=e^{2t}\lt 1, (\cos t+\sin t)^2, (\cos t-\sin t)^2 \gt=3e^{2t} $ $\implies |r'(t)|=\sqrt 3e^{t} $ Need to solve for $t$ $e^t=\dfrac{s}{\sqrt 3}+1;\\t=\ln (\dfrac{s}{\sqrt 3}+1)$ After solving, we get $r(s)=(\dfrac{s}{\sqrt 3}+1) \lt 1, \sin (\ln (\dfrac{s}{\sqrt 3}+1)), \cos (\ln (\dfrac{s}{\sqrt 3}+1)) \gt$
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