Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 15 - Differentiation in Several Variables - 15.6 The Chain Rule - Preliminary Questions - Page 808: 4

Answer

(b)

Work Step by Step

By using the chain rule, we have $$ \frac{\partial f}{\partial r}=\frac{\partial f}{\partial x}\frac{\partial x}{\partial r}+\frac{\partial f}{\partial y}\frac{\partial y}{\partial r}. $$ See the summary on page 807 of the book. Thus, the correct answer is (b).
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