Let a Spherical Triangle have sides of length , , and , and Semiperimeter . Then the Spherical Excess is given by
See also Girard's Spherical Excess Formula, Spherical Excess,Spherical Triangle
References
Beyer, W. H. CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press, p. 148, 1987.