# The Law of Cosines in Spherical Trigonometry

Let *A,B,C* be the vertex angles of a spherical
triangle on the unit sphere, and *a,b,c* the
lengths of the opposite sides, measured by the
angles they subtend at the center.
SPHERICAL LAW OF COSINES:

cos*a* = cos*b* cos*c* + sin*b* sin*c* cos*A*.
(There is also the

SPHERICAL LAW OF SINES:

sin*a* / sin*A* = sin*b* / sin*B* =
sin*c* / sin*C*.)

Back to Bimary Tetrahedral Main Page

Back to Tony's Home Page