Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 3 - Derivatives - 3.9 Derivatives of Logarithmic and Exponential Functions - 3.9 Exercises - Page 211: 51

Answer

$$y = x\sin \left( 1 \right) - \sin \left( 1 \right) + 1$$

Work Step by Step

$$\eqalign{ & f\left( x \right) = {x^{\sin x}};\,\,\,\,\,\,{\text{at the point }}x = 1 \cr & {\text{Use }}{b^x} = {e^{x\ln b}},{\text{ then}} \cr & f\left( x \right) = {e^{\sin x\ln x}} \cr & {\text{Differentiating}} \cr & f'\left( x \right) = {e^{\sin x\ln x}}\frac{d}{{dx}}\left[ {\sin x\ln x} \right] \cr & {\text{Use the product rule}} \cr & f'\left( x \right) = {x^{\sin x}}\left[ {\sin x\left( {\frac{1}{x}} \right) + \ln x\left( {\cos x} \right)} \right] \cr & {\text{Multiply}} \cr & f'\left( x \right) = \frac{{{x^{\sin x}}\sin x}}{x} + {x^{\sin x}}\ln x\cos x \cr & \cr & {\text{Evaluate the function at }}x = 1 \cr & f\left( 1 \right) = {1^{\sin 1}} \cr & f\left( 1 \right) = 1 \cr & {\text{Calculate the slope at }}x = 1 \cr & f'\left( 1 \right) = \frac{{{1^{\sin 1}}\sin 1}}{1} + {1^{\sin 1}}\ln 1\cos 1 \cr & f'\left( 1 \right) = \sin \left( 1 \right) \cr & {\text{The equation of the tangent line is}} \cr & y - {y_1} = m\left( {x - {x_1}} \right) \cr & y - 1 = \sin \left( 1 \right)\left( {x - 1} \right) \cr & y = x\sin \left( 1 \right) - \sin \left( 1 \right) + 1 \cr} $$
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