Integrate using trigonometric identities (#568)

Integrate using trigonometric identities (#568)

Use sin⁡2x=1−cos⁡2x2\sin^2 x = \frac{1-\cos2x}{2}, cos⁡2x=1+cos⁡2x2\cos^2 x = \frac{1+\cos2x}{2}, or substitution.