Unit 2: World of Polygons Part 1
Lesson 4
Exterior Angles
Name_______________________
Date________________________
Exterior Angles of Triangles: Today we will be looking at the angles formed by a side and an extension of a
side. These angles are called exterior angles.
DISCOVERY 1: In each of the following triangles, measure each of the labeled angles.
1)
Measure of ∠1
1=
Measure of ∠2=
Measure of ∠3=
Measure of ∠4=
2)
Measure of ∠1=
2
Measure of ∠2=
Measure of ∠3=
3
4
1
Measure of ∠4=
3.)
Measure of ∠1=
Measure of ∠2=
4 3
Measure of ∠3=
Measure of ∠4=
1
2
Algebraic Proof
1. What do we know about m∠ 1 + m∠ 2 + m∠ 3?
2. What do we know about m∠ 3 + m∠ 4?
3. How can you use this information to prove the hypothesis?
1
2
3
4