Congruent triangles  Why SSA does not work
Math Open Reference

Congruent triangles  Two sides and included angle. SAS
Math Open Reference

Polygons are congruent when all corresponding sides and interior angles are congruent.
Math Open Reference

Definition and properties of the inscribed angle of a circle
Math Open Reference

Definition and properties of vertical (or opposite) angles
Math Open Reference

Definition and properties of supplementary angles  two angles that add to 180 degrees
Math Open Reference

Definition and properties of the interior angles of a transversal
Math Open Reference

Definition and properties of the exterior angles of a transversal
Math Open Reference

Definition of a straight angle. An angle that exactly 180 degrees  a straight line.
Math Open Reference

Definition of an right angle (one whose measure is exactly 90 degrees).
Math Open Reference
