Calculus 8th Edition

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

Chapter 13 - Vector Functions - 13.1 Vector Functions and Space Curves - 13.1 Exercises - Page 894: 39

Answer

The function lies on a cone.

Work Step by Step

We have: \[ x=(1+\cos16t)\cos t, \quad y=(1+\cos16t)\sin t, \quad z=(1+\cos16t) \] Let \(a=(1+\cos16t)\): \[ x=a\cos t, \quad y=a\sin t, \quad z=a \] Squaring each component: \[ x^2=(a\cos t)^2, \quad y^2=(a\sin t)^2, \quad z^2=a^2 \\ x^2=a^2\cos^2 t, \quad y^2=a^2\sin^2 t, \quad z^2=a^2 \\ \] Manipulating \(x^2+y^2\): \[ x^2+y^2=a^2(\sin^2t+\cos^2t) \] Since \((\sin^2t+\cos^2t)=1\), we have: \[ x^2+y^2=a^2 \] Additionally, \(z^2=a^2\) so: \[ x^2+y^2=z^2 \] This represents a cone oriented along the \(z\)-axis.
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