1. Warmup
Triangle Sum Theorem – if you add up the measures of all interior angles of any triangle, you will get 180⁰
For each triangle, find the measure of angle 1:

2. Warmup

3. Warmup

4. Classifying Triangles by Sides and by Angles Part 2
Chp 5.1

5. Triangle Sum Theorems
Triangle Sum Theorem – if you add up the measures of all interior angles of any triangle, you will get 180⁰
Corollary to the Triangle Sum Theorem – the acute angles of a right triangle are complementary (add up to 90⁰)

6. Triangle Angle Measures & Theorems
Exterior Angle Theorem – the measure of an exterior angle = sum of measures of the two non-adjacent interior angles

7. Properties of Triangle Congruence
Reflexive -
ΔABC ΔABC
Symmetric -
If ΔABC ΔDEF, then ΔDEF ΔABC
Transitive -
If ΔABC ΔDEF and ΔDEF ΔJKL, then ΔABC ΔJKL

8. Examples: Corollary to the Triangle Sum Theorem

9. Example: Exterior Angle Theorem

10. Example: Using Everything You Know
Find all the numbered angles: