Learn more: http://www.khanacademy.org/video?v=CbUx0S8BCtA
Solving a definite integral with substitution (or the reverse chain rule)

Length: 7 minutes

Integrals: Trig Substitution 1

Length: 8 minutes

Integrals: Trig Substitution 2

Length: 17 minutes

Integrals: Trig Substitution 3 (long problem)