Foundations of Mathematics 11
Unit 2 Properties of Angles and Triangles
Lesson 2
Angles Properties in Triangles
2.1 Triangle Properties
Angle sum of a Triangle
Scalene Triangles
B
96
A
54
C
?
C
54
A
30
96
B
C 
Isosceles
Y
50
X
65
65
Z
B
If BA  BC
then _____________________
A
C
Reason __________________________________________________
B
If A  C
then _____________________
Reason __________________________________________________
A
Lesson 2
C
Page 1 of 4
Unit 2
Equilateral Triangles
M
N
What is the measure of each angle?
P
2.2 Angle Sum of a Triangle
Example 1. Determine the measure of 1 and 2 .
Example 2. Determine the measure of 1 and 2 .
2.3 Exterior-Interior Angles
Name all interior angles.
Name all exterior angles.
Lesson 2
Page 2 of 4
Unit 2
Non-Adjacent Interior Angles
Example 3
a) Name the non-adjacent interior angles to a and b .
b) Name the non-adjacent interior angles to 1 and 3 .
2.4 Relationship – Exterior-Interior Angles
What can you conclude about 1 and 4  3 ?
PROPERTY:
Example 4
Lesson 2
Prove d  a  b
Page 3 of 4
Unit 2
2.5 Finding Unknown Angles
Example 5
Find the measures of the indicated angles. Give reasons
for your answers.
2.6 More Unknown Angles
Example 6 Find the measures of angles 1, 2, 3, and 4.
Lesson 2
Page 4 of 4
Unit 2