nice-calculus-evaluate-n-1-1-n-n-2-1-sin-n-n-2-

Question Number 129651 by mnjuly1970 last updated on 17/Jan/21

\dots n i c e c a l c u l u s \dots

e v a l u a t e ::

\underset{n = 1}{\sum^{\infty}} \frac{{(- 1)}^{n}}{n^{2} + 1} {(\frac{s i n (n)}{n})}^{2} = ?