Lesson 4-9: Isosceles and Equilateral Triangles Rigor: Use and apply properties of isosceles and equilateral triangles Relevance: Triangle properties are used in architecture, construction, and art.

Notes: Isosceles Triangles Isosceles triangles have at least 2 ≅ sides. Parts: Isosceles Triangle Theorem – If 2 sides of a triangle are congruent, then the angles opposite them are congruent.

Notes: Isosceles Triangles continued The converse is also true! Isosceles Triangle Theorem Converse: If 2 angles of a triangle are congruent, then the opposite sides are also congruent. We will prove both of these theorems later in the chapter using congruent triangles.

Equilateral Triangle Theorem A triangle is equilateral if and only if it is equiangular. AND

Examples: Applying the triangle theorems

Examples continued: What is CB?

4-9 Classwork (not graded) Workbook page 181 #1 – 6 Be ready to discuss answers in 10 minutes

Primary Assignment: join.quizizz.com Codes: 4-9 Honors Assignments Primary Assignment: join.quizizz.com Codes: Period 1 – 437027 (due Thursday) Period 5 – 333308 (due Thursday) Period 6 - 394240 (due Friday) Secondary Assignment: Workbook pg183 #3 – 10, pg184 ALL

4-9 Standard Assignments Primary Assignment: join.quizizz.com Codes: Period 2 – 443320 (due Friday) Period 4 – 371456 (due Friday) Period 7 - 001811 (due Thursday) Secondary Assignment: Workbook pg183 #3, 4, 6 – 10, pg184 ALL