## The Cosine Rule

We can use the cosine rule to:

| 1.Find a side when it is opposite a known angle and that angle is between two known sides. |

| 2. Find an angle when all three sides are known. |

| 1. We start by labelling the sides a,b,c and the angles A,B,C with sides opposite their respective angles as shown. |

| 2. We start by labelling the sides a,b,c and the angles A,B,C with sides opposite their respective angles as shown. |