1. What theorems apply to isosceles and equilateral triangles?
Aim: C A K B
Do Now:
Given:
Prove:
Statements
Reasons 1) 2) 3) 4) 5) 6)
Given
Given
Def. angle bisector
Reflexive Postulate

2. Isosceles Triangle Theorem:
The Base angles of an isosceles triangle are congruent. Q V T E Z M G P D ) ) )
Corollary :
The bisector of the vertex angle of an isosceles triangle bisects the base.
Corollary : )
The bisector of the vertex angle of an isosceles triangle is perpendicular to the base. x
In other words: The median, altitude and angle bisector from the vertex of an isosceles triangle are all the same segment.

3. Equilateral Triangles
Corollary :
Every equilateral triangle is equiangular. A B C Or A B C Or A B C ) ) ) B C )

4. Ex: Isosceles Triangles
If the following pairs of segments are congruent, which angles are congruent. F T D L K Q

5. Algebra w/Isosceles Triangles

6. Ex: Proof w/Isosceles TriangleK M T R A V
Ex: Proof w/Isosceles Triangle
Given:
Prove:
Statements
Reasons 1) 2) 3) 4) 5) 6) 7)
Given
Given
Def. Of midpoint
Given
Geometry Lesson: Isosceles and Equilateral Triangle Theorems

7. Proofs w/Isosceles TrianglesV D
Proofs w/Isosceles Triangles
1) Given:
Prove: M G x D H y T
2) Given:
Prove: A Q E L P N
3) Given:
Prove: