The cosine rule is a great method to use when you have nothing but the sides of a triangle when combined with the 180 degree method. It can also be combined with both the sine rule and the 180 degree rule on a triangle with an angle between 2 sides.
Sides - a² = b² + c² - 2bc cos(A)
Angles - cos(A) = (b² + c² - a²) ÷ 2bc
Komen