Question

2 cos ^2 6 is identical to :

a) 1- cos 12
b) 1 + cos 12
c) 1+ cos 3
d) 1/2 sin ^2 6

Answer 1

cos^2 (x) = (1 + cos(2x))/2 or
2cos^2 (x) = (1 + cos(2x))

now, what will happend if you replace x = 6 to both sides?