The Compendium Geometry is an eBook providing facts, formulas and explanations about geometry.

Law of Cosines, Sines and Tangents

Law of Cosines:

The law of cosines is a generalization of the Pythagorean theorem to general triangles (which need not be necessarily right triangles):

a2 = b2 + c2 - 2bccos α
b2 = a2 + c2 - 2accos β
c2 = a2 + b2 - 2abcos γ

Law of Sines:

The ratios of the lengths of the sides is corresponding to the ratio of the opposite angles:

a : b : c = sin α : sin β : sin γ
with R being the radius of the circumcircle.

Law of Tangents:

Last Update: 2011-01-11