Cosine Rule

🎬 Video Tutorial

Cosine Rule: Use it to find missing sides or angles in non-right-angled triangles.
Cosine Rule Formula: For any triangle, the formula is: a² = b² + c² – 2bc×cos(A), where A is the angle opposite side a.
Finding a Missing Side: If two sides and the included angle are known, plug values into the Cosine Rule to solve for the third side.
Finding an Angle with the Cosine Rule: Rearrange the formula to find the cosine of an angle when all three sides are known.