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.
