1. Lesson 4-5: 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. Concept Byte: paper folding conjectures (pg 265)
If 2 sides have the same length, what is the relationship to the angles opposite the congruent sides?
If 2 angles have the same measure, what is the relationship to the sides opposite the congruent angles?
If you fold the triangle so that the congruent angles map onto each other, what special segment of the triangle is the fold?

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

4. 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.
Both theorems can be proven with congruent triangles.

5. EX 1: Which theorem proves the statement is true?
𝑅𝑇 ≅ 𝑆𝑇
Angle V ≅ angle S

6. Theorem: If a line bisects the vertex angle of an isosceles triangle, then the line is also the perpendicular bisector of the base.
Ex 2: What is the value of x?

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

8. EX 3:

9. 4-5 Classwork and Homework
workbook pg 107 #1-5, 13-18
4-5 Homework: Due Friday
pg 269 #4, 8, 10 – 13, 19, 21, 23, 26