Given tan of theta = -2 and pi/2; find cos(2theta)

[D]  cos2θ = - 3/5

Given tan of theta = -2 and pi/2; find cos(2theta)
The identity of cos (2 theta)=
Given tan of theta = -2 and pi/2.
So, let's plug in tan theta= -2

= (Squaring)
= (simplifying)
So, cos ( 2 theta) = -3/5.
Now we can plug in tan theta = π/2

= (Squaring)
= Simplifying
So, cos ( 2 theta)= -3/5 and (4-pi^2)/(4+pi^2)