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