Evaluate the definite integral by substitution, using Way 2.
We do the substitution first, remembering that this includes changing the limits of integration. Take
We introduce a factor of 4 to the integrand in order to start the substitution.
We still need to change the limits of integration. When we have
and when x = π we have
After we change the limits of integration, the substitution is complete:
Now we can use the FTC to evaluate the integral.