Problem: Evaluate the integral
Solution: This looks like a simple integral. It fits the box "trigonometric integrals" and we see right away that there is an extra sine. This means that the cosine substitution will work; it will change this integral into an elementary one:
To get some practice, we try it another way. The expression in the integral
is of the form
The next step is to use identities and rewrite the product as a sum. The rest is easy using linear substitution.
Is it the same answer as before? Yes.