CCSS IP Math II 5.5.1 Example 4

Author:: Walch Education, GeoGebra Materials Team

Prove that vertical angles are congruent given a pair of intersecting lines,

and

.

GeoGebra Applet

Draw a diagram and label three adjacent angles.
Start with the Supplement Theorem.
Use substitution.
Use the Reflexive Property.
Use the Subtraction Property.
Use the definition of congruence.