AAA Theorem

Specifying three Angles $A$, $B$, and $C$ does not uniquely define a Triangle, but any two Triangles with the same Angles are Similar. Specifying two Angles of a Triangle automatically gives the third since the sum of Angles in a Triangle sums to 180° ($\pi$ Radians), i.e.,

$$C=\pi-A-B.$$

See also AAS Theorem, ASA Theorem, ASS Theorem, SAS Theorem, SSS Theorem, Triangle