Determine whether the series is convergent or divergent.

[Sabricd]

Hello,

I have to determine whether the series converges or diverges.

It is $$\Sigma$$ (-1)^n * cos(Pi/n) where n=1 and goes to infinity.

First I took the absolute value of the function and got the limit from n to infinity of cos(pi/n) and as a result I got 1 because cos(0)=1. However my textbook says it's divergent. Could you please help me understand why it is divergent?

Thank you!

 

[Sabricd]

Nevermind! I figured out why. I guess I confused the alternating series test with some other one. :)

Thanks!