Triangle area from two sides and the included angle: ½ab sin C
Area = ½ab sin C gives a triangle's area from two sides and the angle between them. It is the familiar ½ × base × height with b sin C standing in for the height. The angle must be the included one - the one between the two sides you used.
area
Related Area identities
Practise it
Reading a formula is not the same as recalling it under time pressure. The workspace drills Area questions in the quiz, and the triangle solver shows a worked solution for any triangle you type in.
Or browse all 45 identities in the full reference, or read the trigonometry guides for the method behind them.