Math 8: Triangles and Angle Measures
Section #7: Interior Angles of Triangles
Corresponds with Module 2 Lesson 13
Notes # 39
_________________________
Introductory vocabulary
- An angle whose measure is greater than 0° but less than 90°.
- An angle whose measure is greater than 90° but less than 180°.
- An angle whose measure is exactly 90°
Straight Angle: an angle whose measure is exactly __________, a straight line.
OR
Supplementary Angles: Two or more angles that form a ____________________, meaning that the
sum of the angles is____________.
 INTERIOR ANGLES of a triangle are the angles ________________ the triangle.
 The interior angles of a triangle form a __________________________.
 Therefore, the interior angles of a triangle are _______________________.
<x + <y + <z = _________
Example#1: Find the measure of x
using an equation.
Example#2: Find the measure of each
angle of ABC
Example#3: In triangle ABC, the m<B is twice the m<A and the m<C is 9˚ less than 4 times the m<A.
Find the measure of each angle.
You Try
1) Find the measure of b
using an equation.
2) Find the measure of each
angle of ABC
A
C
B
3) In triangle ABC, the m<A is 3 times the m<B and the m<C is 10˚ more than the m<B. Find the
measure of each angle.
Name:
Section #7: Angle Sum of Triangles: 8.G. 5.
Math 8
HW 32
using an equation.
Find the measure of JFK
J
F
K
U
O
F
Find the measure of UFO
5) The measure of one angle of a right triangle is 74, what are the measures of the other two angles in
the triangle? Show your work using an equation.
6) The measure of one angle of a triangle is 100. If the other two angles of the triangle are
congruent, what are their measures? Show your work using an equation.
7) One angle of a triangle measures 34. A second angle measures 81. What is the measure of the
third angle of the triangle? Show your work using an equation.
a) 65
b) 99
c) 115
d) 146