- #1
Mr Davis 97
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Homework Statement
Find the Maclaurin series and inverval of convergence for ##f(x) = \log (\cos x)##
Homework Equations
The Attempt at a Solution
I used the fact that ##\log (\cos x) = \log (1+ (\cos x - 1))##, and the standard expansions for ##\cos x## and ##\log (x+1)## to get that ##\displaystyle \log (\cos x) = -\frac{x^2}{2} + \frac{x^4}{12} - \frac{x^6}{720} + O (x^8)##. How do I find the interval of convergence for this? Also, how do I know that this is the valid expansion?