What is the

value of 2npie

The answer to this problem is 6.28.

The Correct Answer to your problem is 6.28

Depends on the value of n. If n is even, cos (n*pi) = cos (0) = 1 If n is odd, cos (n*pi) = cos (pi) = - 1

cos (0) = 1 When you make 1 full 2pi rotation, you end up at the same place. So cos (2*n*pi) = cos (0) = 1.