Page 126 - Math Course 2 (Book 2)

Classifying Triangles

isosceles triangle
A triangle with two equal sides. Let’s Begin
The angles opposite the equal 36°
sides are also equal.
d d Classify Angles

Example

72° 72° Classify the angle as acute, obtuse, right, or
b straight.

equilateral triangle C
A triangle with all three sides K M
of equal length. All the angles 60°
will be 60°. m∠KLM < 90
25°

L
60° 60°
A B Answer ∠KLM is acute.

Key Concept m∠NPQ = 180 Q

P
Classify Triangles N

Acute Triangle Scalene Triangle Answer ∠NPQ is straight.

40°
80° m∠RST > 90 R T
60° 115°

all acute angles no congruents sides S
Obtuse Triangle Isosceles Triangle
Answer ∠RST is obtuse.

30°
Classify Triangles

110° 40° at least two Example
one obtuse angle sides congruent
Right Triangle Equilateral Triangle Classify the triangle by its angles and by its sides.

Angles All angles are acute. 60°
Sides All sides are congruent.

60° 60°
45° 45°
The triangle is an acute
Answer
one right angle all sides congruent equilateral triangle.

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