# Chapter 2 - Section 2.2 - Indirect Proof - Exercises - Page 80: 11

We would use the indirect method to prove (a), (b), and (e)

#### Work Step by Step

(a) Let $~~m\angle A \gt m\angle B$ Assume that $AC = BC$ This would lead to a contradiction. We would prove this statement with the indirect method. (b) Suppose these two exterior angles are not congruent. Assume that $l$ is parallel to $m$ This would lead to a contradiction. We would prove this statement with the indirect method. (c) We would prove this statement directly. (d) We would prove this statement directly. (e) Assume that perpendicular bisectors of a line segment are not unique. This would lead to a contradiction. We would prove this statement with the indirect method.

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