To answer this question you need to know a couple important Trigonometric Identities.
1
--- Pythagorean(most important)
2.
3.

The first step is realising that
is the same as
. And you also have to realize that
is the same as
. So, we can deduce that:

The second step is eliminating the 1, and the rest is common sense, we get a common denominator, use our pythagorean theorem of Trigonometry, and flip the fraction to get:

I am sorry for using x and "∅" interchangably.
The full steps are in the attachment.