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.
Related Area identities
Common questions
What is the SAS area identity?
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.
When do you use the SAS area identity?
The angle must be the included one - the one between the two sides you used.
Which identities are related to SAS area?
SAS area belongs to the Area group. The identities used alongside it most often are Heron's formula.
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.