Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 14 - Section 14.3 - Partial Derivatives - 14.3 Exercise - Page 925: 56

Answer

$T_{rr}=4e^{-2r}cosθ$ $T_{θθ}=-e^{-2r}cosθ$ $T_{rθ}=T_{θr}=2e^{-2r}sinθ$

Work Step by Step

Take the first partial derivatives of the given function. When taking partial derivative with respect to r, treat θ as a constant, and vice versa: $T_{r}=-2e^{-2r}cosθ$ $T_{θ}=-e^{-2r}sinθ$ Then take the derivative of the first order partial derivatives to find second partial derivatives: $T_{rr}=4e^{-2r}cosθ$ $T_{θθ}=-e^{-2r}cosθ$ Second partial derivatives of first order partial derivative of r with respect to θ and θ with respect to r are the same: $T_{rθ}=T_{θr}=2e^{-2r}sinθ$
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