Evaluate the following integrals:

We know d(cosx) = sinx, and tan can be written interms of cos and sin

∴

∴ The given equation can be written as

⇒

⇒

Now assume cosx = t

d(cosx) = - dt

sinx dx = - dt

Substitute values of t and dt in above equation

⇒

⇒

⇒

⇒

⇒