Math Playground
Algebra

Sine & cosine laws

Triangles without right angles — two laws that solve them anyway.

Two laws that solve any triangle — not just right ones.

Law of sines
a/sinA = b/sinB = c/sinC
Law of cosines
c² = a² + b² − 2ab cosC

Cosine law generalises Pythagoras — when C = 90°, cosC = 0 and you're back to a² + b² = c².