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Lesson 4-R Chapter 4 Review
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Objectives Review Chapter 4
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Vocabulary None new
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Triangle Classification
By Angles Largest Angle Acute < 90 Right = 90 Obtuse > 90 By Sides Number of Equal Sides Scalene None; all different Isosceles Two Equilateral All three Acute Isosceles Acute Equilateral (also equiangular) Obtuse Scalene
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Triangle Congruence ∆ABC ∆LMN
“CPCTC” – corresponding parts of congruent triangles are congruent Angles match by single letter Sides match by two letter groups Order Rules!!! If proving triangles congruent, always mark only one triangle up with S (for sides) and A (for angles) based on the items you have congruent -- that will make it easier to figure out which theorem or postulate applies
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Triangle Congruence Theorems
Post/Thrm Picture Hidden Features SSS Shared Side SAS Vertical Angles // Lines Alt Int ’s ASA AAS S S S S S A A S A A A S
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Hidden Features in Triangle
Picture Triangles by Shared Side SSS Vertical Angles SAS Parallel Sides (lines) Alternate Interior Angles AAS S S S S S A A A S
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Finding the Measures of Angles
Rules for finding measures of angles Linear Pairs sum to 180 Vertical Angles are equal Sum of the angles in a Triangle = 180 Exterior angle = sum of remote interiors Use angle classification to eliminate impossible answers Corner of paper is a 90° angle
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Isosceles Triangle Theorems
Angles opposite congruent sides are congruent Sides opposite congruent angles are congruent
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Summary & Homework Summary: 4 Homework: study for test
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