Alternating Series Test
An alternating series is basically a series whose terms’ signs are changing regularly. They often have the form
$$ \sum_{n=1}^\infty (-1)^n a_n $$
in order for such a series to converge, it needs to satisfy all three of the requirements below:
- It is alternating.
- $|a_{n+1}| < |a_n|$ for all $n$
- $\lim_{n\to\infty} a_n = 0$