Question

Show that by using any formula​

Answer 1

Step-by-step explanation:

Just use

cos(2a) = 2cos^2(a) -1

So let's take look at the term which is inside the root

2+2cos4a = 2+2(2(cos(2a))^2-1) = √cos(2a)^2 = cos2a

Use the same process to get your result

Answer 2

Used, 1+cos2A=2cos²A