First we are going to find the common denominator of both fractions. To do that, we are going to multiply their denominators:
Now we can rewrite our expression using the common denominator:
Finally, we can use the trig identities:
and 
to simplify our trig expression:
We can conclude that the correct answer is the fourth one.
Now we can rewrite our expression using the common denominator:
Finally, we can use the trig identities:
We can conclude that the correct answer is the fourth one.