Talk:Sum of Infinite Series of Product of Power and Sine

Removed the note:

It is noted that when $x$ is a multiple of $2 \pi$ then:

$1 - 2 r \cos x + r^2 = 1 - 2 + 1 = 0$

leaving the right hand side undefined.

This is not accurate since $r \in \R$ such that $\size r < 1$.

Therefore:

$- 2 r \cos x \gt - 2$

Therefore:

$1 - 2 r \cos x + 1 \gt 0$. --Robkahn131 (talk) 01:51, 18 March 2021 (UTC)