1. 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.

2. 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.

3. 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.

4. Example: Which theorem proves the statement is true?
WVS ≅ S
𝑅𝑇 ≅ 𝑆𝑇

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

6. Examples: Applying the triangle theorems

7. Examples continued:
What is CB?

8. 4-9 Classwork and Homework
4-9 Classwork: Core book pg 181 #1 - 6
4-9 Homework:
Standard: core book pg 183 #3, 4, 6 – 10
Honors: core book pg 183 #3 – 10
Due Thursday for periods 1, 3, 5
Due Friday for periods 2, 4, 7