What is the approximate length of the third side of the triangle below?
22.2 mm
25.8 mm
35.5 mm
46.1 mm

You need the Law of Cosines here.  Let's call our given angle A, so the side across from it, the one we are looking to solve for, would be a.  The Law is as follows then: .  We will simplify everything here at once to get .  so a = 35.5