Classify

1. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
Chapter 4: Congruent Triangles
Activity: Find the sum of the measures of the angles.
Materials: Paper, Ruler & Scissors
Draw 2 different sized triangles with one of the sides extended.
Label the 4 angles. Cut out the triangles.
1st Triangle: Tear off the three corners. Place them next to each
other on the extended line.
Make a conjecture about the sum of the measures of interior <s
2nd Triangle: Tear off corners that aren't next to the exterior <s.
Use them to fill the exterior <.
Make a conjecture about the relationship between the measure of
an exterior < and the nonadjacent interior <s.
A
B C D
W
X Y Z
Conclusions:
The sum of the measures of the interior <s of a triangle = 180.
The measure of the exterior angle of a triangle the sum of the 2
nonadjacent interior <s.

2. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
4­1
Triangle Sum Properties
Objectives:
To understand the sum of the measures of the angles of a
triangle.
Classify Triangles by Sides
Scalene Isosceles Equilateral
Classify Triangles by Angles
Acute Right Obtuse Equiangular

3. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
Triangle Sum Theorem
The sum of the measures of the angles in every triangle is _____.
xo x = ______
54o 39o
no
135o 30o
n = ______

4. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
Exterior Angle Theorem
The measure of an exterior < of a triangle = the sum of the measures of the 2
nonadjacent interior <s.
1
2
3
Exterior
Angle
Nonadjacent
Interior
Angles
Corollary to the Triangle Sum Theorem
The acute angles of a right triangle are complementary.
A
B C
<A + <C = 90

5. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
Find the measure of each numbered angle in the figure.
120o
78o
50o
56o
1
2
3
4 5
95o
33o
109o
24o
1
2 3

6. 4.1 Classifying Triangles
HW pg. 221 #8­18
evens, 21­26,
32, 36
October 14, 2014
HW
pg. 221
#8­18
evens,
21­26,
32 & 36