Math basics › Trigonometry
Laws of sines and cosines
Law of sines
a/sin A = b/sin B = c/sin C. Use when you have an angle paired with its opposite side.
Law of cosines
c² = a² + b² − 2ab cos C. Use for three sides, or two sides and the angle between them. Pythagoras is this with C = 90°.
The ambiguous case
Two sides and a non-included angle can describe two different triangles. Check whether the second one is possible.