Download 5_2 Triangle Sum Theorem

Just for fun…
do these
(on the back of your warm up)
1.
1 2 3
2.
4
5
3.
Name 2 pair of alternate interior angles
5 & 3
and
4 & 1
What is the sum of m1 + m2 + m3?
180°
If m4 = 65° and m5 = 50°, what is
m2?
65°
90
°
50
°
130
50°
°
40
°
40 50
°90°
°
40
°
4.
Find all the angle measures
Just a little quickie…
♥ Please get pg 173 off the front desk and
do problems 5-20….
♥ We’re just getting a head start on today’s
assignment…
♥ We’ll have notes in 15 minutes…
♥ Go
5.2
Triangle Sum Theorem
&
Exterior Angle Theorem
Objectives---What we’ll learn…
• Find the measurement of a missing angle
by using Triangle Angle Sum Theorem.
• Find the measurement of a missing angle
by using Exterior Angle Theorem.
Triangle Sum Theorem
The sum of the angle measures in a triangle
equal 180°
1
3
2
1 + 2 + 3 = 180°
Isosceles Triangles
2 congruent sides
2 congruent base angles
Isosceles Triangles & Angle Sum Theorem
Base Angles are congruent.
W  H
E + W + H = 180o
E + 2(W) = 180o
Exterior Angle Theorem
The measure of an exterior angle in a
triangle is the sum of the measures of
the 2 remote interior angles
exterior
angle
remote
interior
angles
A = C + D
Exterior Angle Theorem
The measure of an exterior angle in a
triangle is the sum of the measures of
the 2 remote interior angles
remote
interior
angles
exterior
angle
2
1
3
4 = 1 + 2
4
Example 1 on Exterior Angle
Example 2 on Exterior Angle
Example 3 on Exterior Angle
(more challenging)
Example 4 on Exterior Angle
(more challenging)
Shortcut:
1. Triangle INTERIOR Angle Sum
Interior 1
+ Interior 2 + Interior 3
= 1800
= 1800
2. Triangle EXTERIOR Angle Sum
Remote Interior
1
+ Remote Interior
2
= Exterior Angle
= Exterior Angle
an example with numbers
find x & y
82°
x = 68°
30°
x
y
30x
40x
y = 112°
find all the angle measures
10x2
80°, 60°, 40°
Do you hear the
sirens?????
Finish
the
assignment