You can use a
substitution after the simplification but it's not that necessary IMHO.
After the
sub, you end up with
. If we see patterns in the integrals of trigonometric functions, this is easy to integrate.
. It can be deduced that
. A similar relationship applies for
and
. These relationships are very useful when determining integrals of trig functions. It's very nice how you can 'co' all the functions and then put a minus sign out the front - if you know what I mean.
Additionally,
Looks similar to the trig identities?
+Cs, obviously.