# Maclaurin Series used to find associated radius of convergence Q!

 P: 85 I have the Maclaurin series for cos (x), is their a way to find its radius of convergence from that? ALSO Is there a trick to find the shorter version of the power series for the Maclaurin series, I can never seem to find it so instead of the long series with each term but like E summation (the series)
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P: 1,994
 Quote by badtwistoffate I have the Maclaurin series for cos (x), is their a way to find its radius of convergence from that?
you can try the ratio test.

 Quote by badtwistoffate ALSO Is there a trick to find the shorter version of the power series for the Maclaurin series, I can never seem to find it so instead of the long series with each term but like E summation (the series)
Err, do you mean writing the series using the sigma notation instead of the first few terms followed by some ...? You want to look for patterns in the coefficients. No real trick, practice will help though.
P: 85
 Quote by shmoe you can try the ratio test. Err, do you mean writing the series using the sigma notation instead of the first few terms followed by some ...? You want to look for patterns in the coefficients. No real trick, practice will help though.
Yeah i tried the ratio test, but the radius of convergence it sayed in the big is infinity, how is that possible as it has to be n < 1?