Calculus: Early Transcendentals (2nd Edition)

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

Chapter 7 - Integration Techniques - 7.2 Integration by Parts - 7.2 Exercises - Page 521: 53

Answer

$$\left( {\tan x + 2} \right)\ln \left( {\tan x + 2} \right) - \tan x + C$$

Work Step by Step

$$\eqalign{ & \int {\left( {{{\sec }^2}x} \right)\ln \left( {\tan x + 2} \right)} dx \cr & \int {\ln \left( {\tan x + 2} \right)\left( {{{\sec }^2}x} \right)} dx \cr & {\text{Let }}t = \tan x + 2,{\text{ }}dt = {\sec ^2}xdx \cr & \cr & {\text{Apply the substitution}} \cr & \int {\ln \left( {\tan x + 2} \right)\left( {{{\sec }^2}x} \right)} dx = \int {\ln t} dt \cr & \cr & {\text{Use the Integral of }}\ln x\left( {{\text{See page 519}}} \right):{\text{ }} \cr & \int {\ln xdx} = x\ln x - x + C,{\text{ then}} \cr & \int {\ln t} dt = t\ln t - t + C \cr & {\text{Back - substitute }}t = \tan x + 2 \cr & = \left( {\tan x + 2} \right)\ln \left( {\tan x + 2} \right) - \left( {\tan x + 2} \right) + C \cr & = \left( {\tan x + 2} \right)\ln \left( {\tan x + 2} \right) - \tan x - 2 + C \cr & {\text{Combine constants}} \cr & = \left( {\tan x + 2} \right)\ln \left( {\tan x + 2} \right) - \tan x + C \cr} $$
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