Sine & Cosine Rules and Area of a Triangle

Solve any triangle — not just right-angled ones — using the sine rule, cosine rule, and the ½ab sin C area formula.

Area of a Triangle Using ½ab sin C

Calculate the area of any triangle when two sides and the included angle are known, using the sine area formula.
The Cosine Rule

Use the cosine rule to find a missing side or angle when you have two sides and the included angle, or all three sides.
The Sine Rule

Apply the sine rule to find unknown sides or angles in non-right-angled triangles — and know when to use it.