Angle DAB is an exterior angle of the triangle. Angles C and B are the remote interior angles of this exterior angle. You can change the triangle by moving the vertices. Explore until you can answer the following questions. Discuss with your partner, then write your final answers (with a diagram!) in your notebook.
1) What do we mean by the remote interior angles of an exterior angle?
2) What is the relationship between the measures of the exterior angle and its two remote interior angles?
3) WHY do you think they have this relationship?
4) Can you PROVE this relationship from our existing theorems?