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

5. Examples: Applying the triangle theorems

6. Examples continued:
What is CB?

7. 4-9 Assignment from the Workbook
pg 181 #1 – 6
pg 183 #3, 4, 6 – 10 (Honors also #5)
Do not round answers! Leave answers as radicals or fractions where necessary.
Due Thursday 11/17 for periods 1, 5, & 7
Due Friday 11/18 for periods 2, 4, & 6