4.1. Triangle Sums http://www.ck12.org
Example 4:Find the measure of^6 RQS.
Solution: 112 ◦is an exterior angle of 4 RQS. Therefore, it is supplementary to^6 RQSbecause they are a linear pair.
112 ◦+m^6 RQS= 180 ◦
m^6 RQS= 68 ◦If we draw both sets of exterior angles on the same triangle, we have the following figure:
Notice, at each vertex, the exterior angles are also vertical angles, therefore they are congruent.
6 4 ∼= (^67)
6 5 ∼= (^68)
6 6 ∼= (^69)
Example 5:Find the measure of the numbered interior and exterior angles in the triangle.