HG 3
D7. If two angles – BAD and – CAD have a common side AD and the other two
sides AB and AC form opposite rays, the angles are called supplementary angles.
D8. An angle – BAD is a right angle if it has a supplementary angle to which it
is congruent.
A5. All right angles are congruent.
A6. An angle can be constructed congruent to a given angle with preassigned
vertex and side. (This is often referred to as the "angle copier" axiom).
D9. If two angles – BAD and – CAD have a common side AD and – BAD = – CAD, then AD is the angle bisector of – BAC.
A7. Every angle has a bisector.
A8. A thing is congruent to itself.