Calculus (3rd Edition)

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

Chapter 9 - Further Applications of the Integral and Taylor Polynomials - Chapter Review Exercises - Page 497: 28

Answer

$$T_{3}(x) = \frac{-1}{2}x^2$$

Work Step by Step

Given $$f(x)=\ln (\cos x), \quad T_{3}, \quad a=0$$ Since \begin{align*} f(x)&=\ln (\cos x)\ \ \ \ \ \ \ &f(0)=0\\ f'(x)&=\frac{-\sin x}{\cos x}\ \ \ \ \ \ \ &f'(0)=0\\ f''(x)&= -\sec^2 x\ \ \ \ \ \ \ &f''(0)=-1\\ f'''(x)&= -2\sec^2 x\tan x\ \ \ \ \ \ \ &f'''(0)=0 \end{align*} Then \begin{aligned} T_{3}(x)&= f(a)+f^{\prime}(a)(x-a)+\frac{f^{\prime \prime}(a)}{2 !}(x-a)^{2}+\frac{f^{\prime \prime \prime}(a)}{3 !}(x-a)^{3} \\ &= \frac{-1}{2}x^2 \end{aligned}
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.