Question

Sigma n=1 to infinite (-1)^n sin(pi/n)

I confuse about this alternative test

I know this function F(x) = sin(pi/n) should be decreasing for all n value.

but it is not decreasing when n =1 , n=2

but the answer is convergent.

so how I figure out this one, is it okay to ignore when n is 1 or 2? then why? cause the condition said, Function must be decreasing for all n value.

Answer 1