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Lesson 2 - 5

Proving Lines Parallel. Lesson 2 - 5. Proving Lines Parallel - Postulates & Theorems. If two lines are cut by a transversal and corresponding angles are congruent , then the lines are parallel. Proving Lines Parallel - Postulates &Theorems.

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Lesson 2 - 5

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  1. Proving Lines Parallel Lesson 2 - 5 Lesson 2-5: Proving Lines Parallel

  2. Proving Lines Parallel - Postulates & Theorems • If two lines are cut by a transversal and corresponding angles are congruent, then the lines are parallel. Lesson 2-5: Proving Lines Parallel

  3. Proving Lines Parallel - Postulates &Theorems • If two lines are cut by a transversal and alternate interior angles are congruent, then the lines are parallel. Lesson 2-5: Proving Lines Parallel

  4. Proving Lines Parallel - Postulates &Theorems • If two lines are cut by a transversal and consecutive interior angles are supplementary, then the lines are parallel. Lesson 2-5: Proving Lines Parallel

  5. Proving Lines Parallel - Postulates &Theorems • If two lines are cut by a transversal and consecutive exterior angles are supplementary, then the lines are parallel. Lesson 2-5: Proving Lines Parallel

  6. Theorem 3.8 (AIA Converse): If 2 lines are cut by a transversal so that AIA are congruent then the lines are parallel. Proving AIA Converse Given: 1  2 Prove: p q 3 p 1 2 q Statements Reasons 1. 1  2 1. Given 2. Vert. ’s Theorem 2. 1  3 3. Trans. POC 3. 2  3 4. Corres. ’s Converse 4. p q

  7. Theorem 3.9 (CIA Converse): If 2 lines are cut by a transversal so that CIA are supplementary then the lines are parallel. Proving CIA Converse p Given: Angles 4 and 5 are supplementary. Prove: p and q are parallel 6 5 4 q Reasons Statements 1. 4 and 5 are supplementary. 1. Given 2. 5 and 6 are supplementary. • Linear Pair Postulate 3.  Supplements Theorem 3. 4 6 4. p q 4. AIA Converse

  8. 2. 1. 3. 4. Examples: Proving Lines Parallel • Find the value of x which will make lines a and lines b parallel. Answers: 1. 20° 2. 50° 3. 90° 4. 20° Lesson 2-5: Proving Lines Parallel

  9. Ways to Prove Two Lines Parallel • Show that corresponding angles are equal. • Show that alternative interior angles are equal. • Show that consecutive interior angles are supplementary. • Show that consecutive exterior angles are supplementary. • In a plane, show that the lines are perpendicular to the same line. Lesson 2-5: Proving Lines Parallel

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