What is the cosine rule?
What is it?The cosine rule is a tool to find the size of an angle or the length of a side in a triangle.When to use it?- When we are given 2 sides and an angle- When we are given 3 sidesHow?For a triangle with sides a,b and c and angles A, B and C the cosine rule can be written as:a2 = b2 + c2 - 2bc cos Aorb2 = a2 + c2 - 2ac cos Borc2 = a2 + b2 - 2ab cos C
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