Lesson 4-R Chapter 4 Review

Objectives Review Chapter 4

Vocabulary None new

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

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

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

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

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

Isosceles Triangle Theorems Angles opposite congruent sides are congruent Sides opposite congruent angles are congruent

Summary & Homework Summary: 4 Homework: study for test