Verified answer

step-by-step expalination:

we gonna use the following equation

cos2θ = 2cos²θ - 1 (a)

cos2θ + 1 = 2cos²θ (b)

we can write the question as 4cos²θ - 1 using the

(a+b)(a-b) theorem

4cos²θ - 1

=2cos²θ + 2cos²θ - 1

i am gonna substitute the equation (a) for 2cos²θ - 1

and equation (b) for 2cos²θ

=cos2θ + 1 + cos2θ

=2cosθ + 1