1. Triangles and Isoscles
Sum of angles and properties of isosceles

2. Triangle Sum Conjecture
Conjecture – a generalization resulting from inductive reasoning Sum of angles of a triangle =180 Can you prove this without using a protractor

3. This is on page 201
Try and write a proof on why the angles add to 180

4. The proof Statement Reason EC is a line Given AB is parallel to EC
1+2+3=180
def of a line
1=4 AI
3=5
4+2+5=180
Substitution

5. Properties of Angles Remember all the different angle properties
Vertical
Linear Pair AI AE
Corr
SSI

6. Isosceles Triangles 2 congruent sides - legs
2 congruent angles – formed by non congruent sides, base angles
Non Congruent side is called the base
Vertex – non congruent angle, formed by congruent sides

8. If legs are congruent then it is an isosceles triangle If base angles are congruent then it is an isosceles triangle

9. Examples
Find the missing measures

10. Homework
Pg Pg Honors pg