DefinitionOne method of evaluating integrals of square roots of quadratic expressions is through the use of trigonometric substitution. Through substitution of a trigonometric function for the variable the integral is transformed into an easier to calculate trigonometric integral. If math has served me correctly, this is again true, but we can work this to our benefit by using clever trigonometry identities to simplify the integrand. Example: To find ∫1−x2dx, use the substitution x=sinθ. Therefore, dx=cosθdθ⇒ 1−x2=1−sin2θ=cosθ. The integral is,∫cos2θdθ (1)This is solvable with trigonometric identities.