Slide 1

Report
Objective
Classify triangles by their angle measures
and side lengths.
Recall that a triangle ( ) is a polygon
with three sides. Triangles can be
classified in two ways: by their angle
measures or by their side lengths.
Classify by angle measure
Acute
Has three
acute angles
Right
Has one right
angle
Obtuse
Has one
obtuse angle
Equiangular
All angles are
congruent
Classify by Sides
Equilateral
All sides
congruent
Isosceles
At least two
sides
congruent
Scalene
No sides
congruent
Parts of an isosceles triangle
Vertex
Leg
Leg
Base Angle
Base
Base Angle
Remember!
When you look at a figure, you cannot assume
segments and angles are congruent based on
appearance. They must be marked as congruent.
Example
Classify
ACD by its side lengths.
From the figure,
scalene.
. So AC = 15, and
ACD is
Example
Classify
FHG by its angle measures.
EHG is a right angle. Therefore mEHF +mFHG = 90°.
By substitution, 30°+ mFHG = 90°. So mFHG = 60°.
FHG is an equiangular triangle by definition.
Example
Classify
BDC by its angle measures.
B is an obtuse angle.
B is an obtuse angle. So
triangle.
BDC is an obtuse
Homework
Section 3 – 2
# 1-21 all, 22-34 even

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