AMC 10 2001 Problem 20

A regular octagon is formed by cutting an isosceles right triangle from each of the corners of a square with sides of length 2000. What is the length of each side of the octagon?

Answer Choices
A. \dfrac{1}{3}(2000)
B. 2000(\sqrt{2}-1)
C. 2000(2-\sqrt{2})
D. 1000
E. 1000 \sqrt{2}