Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
4. Proofs with Perpendicular Lines
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Exercise 13 Page 525

Use the following figure.

See solution.

Practice makes perfect
In the following figure it's given that ∠ 1 ≅ ∠ 2.


According to the Linear Pair Perpendicular Theorem, if two lines intersect to form a linear pair of congruent angles, then the lines are perpendicular. Thus, using the given information, we want to prove that g ⊥ h. Let's write a two-column proof.

Statement
Reason
1.
∠ 1 ≅ ∠ 2
1.
Given
2.
m∠ 1 = m∠ 2
2.
Definition of congruent angles
3.
m∠ 1+m∠ 2=180^(∘)
3.
Linear Pair Postulate, according to the diagram
4.
m∠ 1+m∠ 1=180^(∘)
4.
Substitution Property of Equality
5.
2m∠ 1=180^(∘)
5.
Distributive Property
6.
m∠ 1=90^(∘)
6.
Distributive Property of Equality
7.
g ⊥ h
7.
Definition of perpendicular lines