Law of Sines and Cosines
Law of Sines
sin A
a
=
sin B
b
=
sin C
c
Law of Cosines
For this (or any given triangle), the Law of Cosines says:
c2 = a2 + b2 − 2ab cos C
This law is helpful if you need to find the angles of a triangle but know all the side lengths, or if you want to solve for the third side of a triangle when you know the lengths of the other two sides and the angle between them.
