Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 4 - Integration - 4.4 Exercises - Page 288: 33

Answer

0

Work Step by Step

$\int$4sec(x)tan(x)dx = 4$\int$sec(x)tan(x)dx remember that $\frac{d}{dx}$[sec(x)] = sec(x)tan(x) therefore 4$\int$sec(x)tan(x)dx = 4sec(x)+C However this is a definite integral so we must evaluate the antiderivative from -$\frac{\pi}{3}$ to $\frac{\pi}{3}$. Both sec(-$\frac{\pi}{3}$) and sec($\frac{\pi}{3}$) are equal to 2. We can then write 4sec($\frac{\pi}{3}$) - 4sec(-$\frac{\pi}{3}$), which simplifies to 4(2)-4(2). Which clearly equals zero. Another way to solve this is graphically. The function has point symmetry about the origin. Therefore if the integral is evaluated from -x to x, it will always equal zero.
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