Question
Show that:
Solution
Let I = 
Put x = cos2 θ, θ dx = 2 cos θ (– sin θ) dθ = – 2 sin θ cos θ dθ = – sin 2θ dθ
When x = 0, 
When x = 1, cos2 θ = 1 ⇒ θ = 0
