Law of Sines circumradius form: a/sin A = 2R
The common ratio in the Law of Sines is not arbitrary: it equals 2R, twice the radius of the triangle's circumscribed circle. That turns the Law of Sines into a way of finding the circumradius from any one side and its opposite angle.
Related Law of Sines identities
Common questions
What is the Circumradius form identity?
The common ratio in the Law of Sines is not arbitrary: it equals 2R, twice the radius of the triangle's circumscribed circle. That turns the Law of Sines into a way of finding the circumradius from any one side and its opposite angle.
Which identities are related to Circumradius form?
Circumradius form belongs to the Law of Sines group. The identities used alongside it most often are Law of Sines.
Practise it
Reading a formula is not the same as recalling it under time pressure. The workspace drills Law of Sines 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.