## Elementary Geometry for College Students (5th Edition)

Published by Brooks Cole

# Chapter 1 - Section 1.7 - The Formal Proof of a Theorem - Exercises: 18

#### Answer

$\angle(1)=133^{\circ}$ $\angle(3)=133^{\circ}$ $\angle(4)=47^{\circ}$

#### Work Step by Step

$\angle(2)$ is supplementary to $\angle(1)$ and $\angle(3)$, and $\angle(2)$ is $47^{\circ}$, so $\angle(1)$ and $\angle(3)$ equal $133^{\circ}$ because $180^{\circ}-47^{\circ}=133^{\circ}$. $\angle(4)$ is supplementary to $\angle(1)$ and $\angle(3)$, and since each angle is $133^{\circ}$, $\angle(4)$ equals 47 because $180^{\circ}-133^{\circ}=47^{\circ}$.

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