After The School
Class 12MathematicsChapter 7: Integrals

7.3 Integration by Substitution

Method of substitution for integrating composite functions, with worked example.

7.3 Integration by Substitution

If the integrand contains a composite function, substitute the inner function.

Example

Evaluate 2xcos(x2)dx\displaystyle\int 2x \cos(x^2)\,dx.

Let t=x2t = x^2, so dt=2xdxdt = 2x\,dx.

2xcos(x2)dx=costdt=sint+C=sin(x2)+C\int 2x \cos(x^2)\,dx = \int \cos t\,dt = \sin t + C = \sin(x^2) + C