Interesting Ways to Find the value of Pi

Question

Is there any interesting ways to find pi?

Thanks.

Answer 1

Try the Gregory Series, It uses a sequence to find the value of Pi

Answer 2

$$ \pi = \sqrt{6(1 + \frac 1{2^2} + \frac 1{3^2} + \frac 1{4^2} + \frac 1{5^2}...)}$$