Question

Question #fcccb

Answer 1

`2cos^2 (2x)`

Explanation:

Let `cos 2x = a`

Then the sum becomes,

`a * 2a = 2a^2`

Replacing a with cos 2x, we get the answer as

`2cos^2 (2x)`

Answer 2

`cos2x*2cos2x=2cos^(2)2x=1+cos4x`