If you want to work it out yourself first here is the trick. Set calculator to degree mode, enter a bunch of fives (5555 or 55555555), take the reciprocal, tak

If you want to work it out yourself first here is the trick. Set calculator to degree mode, enter a bunch of fives (5555 or 55555555), take the reciprocal, take the sin, note similarity to pi. Very fun article.