Objectives Write flowchart and paragraph proofs.

Geometry – Postulates and Paragraph Proofs
Geometry – Postulates and Paragraph Proofs

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Objectives Write flowchart and paragraph proofs.
Prove geometric theorems by using deductive reasoning.

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Vocabulary flowchart proof paragraph proof

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_________________- A second style of proof which uses boxes and arrows to show the structure of the proof. The justification for each step is written below the box.

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Example 1A: Reading a Flowchart Proof
Use the given flowchart proof to write a two-column proof. Given: 2 and 3 are comp. 1 3 Prove: 2 and 1 are comp. Flowchart proof: Two-column proof: Statements Reasons 1. 1. 2. 2. 3. 3. 4. 4. 5. 5.

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Statements Reasons Example 1B
Use the given flowchart proof to write a two-column proof. Given: RS = UV, ST = TU Prove: RT TV Statements Reasons Flowchart proof: 1. 1. 2. 2. 3. 3. 4. 4. 5. 5..

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Example 2A: Writing a Flowchart Proof
Use the given two-column proof to write a flowchart proof. Given: B is the midpoint of AC. Prove: 2AB = AC

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_________________– a style of proof that presents the steps of the proof and their matching reasons as sentences in a paragraph. Although this style of proof is less formal than a two-column proof, you still must include every step.

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Example 3: Reading a Paragraph Proof
Use the given paragraph proof to write a two-column proof. Given: m1 + m2 = m4 Prove: m3 + m1 + m2 = 180° Paragraph Proof: It is given that m1 + m2 = m4. 3 and 4 are supplementary by the Linear Pair Theorem. So m3 + m4 = 180° by definition. By Substitution, m3 + m1 + m2 = 180°. Two-column proof: Statements Reasons 1. 1. 2. 2. 3. 3. 4. 4.

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Example 4A: Writing a Paragraph Proof
Use the given two-column proof to write a paragraph proof. Given: 1 and 2 are complementary Prove: 3 and 4 are complementary m3 + m4 = 90° 3 and 4 are comp. Paragraph proof:

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Example 4B Use the given two-column proof to write a paragraph proof. Given: 1 4 Prove: 2 3 Two-column proof: Paragraph proof:

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