Answer:
When proving identities, the answer is in the explanation.
Step-by-step explanation:
I have two terms in this denominator here.
I also know that by Pythagorean Identity.
So I don't know how comfortable you are with multiplying this denominator's conjugate on top and bottom here but that is exactly what I would do here. There will be other problems will you have to do this.
Big note here: When multiplying conjugates all you have to do is multiply fist and last. You do not need to do the whole foil. That is when you are multiplying something like , the result is just
.
Let's do that here with our problem in the denominator.
In that last step, I apply the Pythagorean Identity I mentioned way above.
Now You have a factor of cos(y) on top and bottom, so you can cancel them out. What we are really saying is that cos(y)/cos(y)=1.
This is the desired result.
We are done.