After making the appropriate inverse trig substitution x=ag(θ) (where g is a certain trigonometric function), the indefinite integral
∫sin(2θ) dθ
is obtained. What integral did we start with?
sin2θ = √(1 - cos^2(2θ)) or 2sinθ cosθ = 2sinθ √(1 - cos^2θ)
so, what do you think?