This week in Math 11, we learned how to use the Cosine Law. To use this method, you need atleast 2 side lengths, an angle or 3 side lengths. The cosine law is used to find an angle, for the first step you have the givens, a, b, and c is what i use. The equation we use for the first method is, c2 = a2 + b2 – 2ab cos C. One thing to keep in mind is that you can have information from the opposite side. For the example below, we used A= 10 cm, B= 18 cm, C= 20cm. Since we’re given three side angles, i used the second method which requires 3 side angles.