The corners of the square, 2m. sides, are cut off to form a regular octagon. What is the length of the side of the resulting octagon?

Answer 1

Let the side length be a.

a + 2*a*(sqrt2)/2 = 2
a = 2/(2.414) = 0.8285 m

See http://mathcentral.uregina.ca/QQ/database/QQ.09.02/rich1.html
for a proof