,
The Substitution method(or 'changing the variable')
This is best explained with an example:
![]()
Like the Chain Rule simply make one part of the function equal to a variable eg u,v, t etc.
![]()
Differentiate the equation with respect to the chosen variable.
![]()
Rearrange the substitution equation to make 'dx' the subject.

Substitute for 'dx' into the original expression.
![]()
Substitute the chosen variable into the original function.
![]()
Integrate with respect to the chosen variable.
![]()
Restate the original expression and substitute for t.
![]()
NB Don't forget to add the Constant of Integration(C) at the end. Remember this is an indefinite integral.
Example #1

Example #2

Example #3
