Triangles with integral sides and circumradius. A general formula giving such triangles was stated by Gauss, we propose to find a general formula giving prime solutions—that is, a formula giving integral sides and circumradius, a, b, c, R , which have highest common factor unity If α β γ are the angles of an integral triangle, then sin α , sin β , sin δ and cos α , cos β , cos γ are rational.