Download Section 7.3 Triangles

Section 7.3 Triangles
Page 1
Complete the following table for the triangles you created with your partner:
a.
b.
c.
40°
m<1
d.
100°
75°
m<2
30°
m<3
Sum of the three angle measurements
What pattern do you see with these three triangles?

The sum of the angle measures of any _____________ is __________.
m<x +m<y + m<z = 180°
Try this:
x°
What is the measure of angle x?
28°
x°
y°
50°
z°
Classifying Triangles

You can use __________ lengths and angle ____________ to classify triangles.
Classifying Triangles using Angles
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A triangle with _________ angles that are acute is called an __________ triangle.
An _______ triangle has _________ angle that is obtuse.
If one angle of a triangle is a __________ angle, the triangle is called a right
____________.
An ___________ triangle has three ____________ angles.
Classifying Triangles using Sides
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A ___________ triangle has no congruent sides.
An isosceles triangle has ______ congruent sides.
An equilateral triangle has 3 _______________ sides.
Section 7.3 Triangles
Page 2
KEY
Complete the following table for the triangles you created with your partner:
a.
b.
c.
d.
m<1
40°
60°
90°
100°
m<2
70°
75°
30°
40°
m<3
70°
45°
60°
40°
Sum of the three angle measurements
180°
180°
180°
180°
What pattern do you see with these three triangles?

The sum of the angle measures of any triangle is 180°.
The measure of angle x in the Try This: is 94°.
Classifying Triangles
You can use side lengths and angle measures to classify triangles.
Classifying Triangles using Angles




A triangle with all angles that are acute is called an acute triangle.
An obtuse triangle has one angle that is obtuse.
If one angle of a triangle is a right angle, the triangle is called a right triangle.
An equiangular triangle has three congruent angles.
Classifying Triangles using Sides



A scalene triangle has no congruent sides.
An isosceles triangle has 2 congruent sides.
An equilateral triangle has 3 congruent sides.