Which expression is equivalent to cos 2 pi for all values of pi?

A) cos2pi + sin2pi

B) cos2pi - 1

C) 1 - 2 sin2 pi

D) 2 sinpi cospi

In radians, pi = 180 degree, Hence for 2pi = 360 degree.

For cos 0 = cos 2pi = 1

And

Sin 0 = sin 2pi = 0

While cospi = - 1 and sinpi = 0

So

A) cos2pi + sin2pi = 1 + 0 = 1

B) cos2pi - 1 = 1 - 1 = 0

C) 1 - 2sin2pi = 1 - 2 (0) = 1

D) 2 sinpi cospi = 2 * 0 * (-1) = 0

Hence "A" and "C" are correct.