THE TRUTH ABOUT TRIANGLES

HOW MANY SIDES ARE THERE, AND

WHAT IS THEIR ANGLE?

There are two ways to classify triangles:By their sides

By their angles

Classifying Triangles by their sidesThere are three types:

ScaleneIsoscelesEquilateral

1. SCALENENo congruent sides (No sides are equal)

12in.

2. ISOSCELESTwo of the sides are congruent, (equal)

5 in.

10 in.

10 in.

3. EQUILATERAL SIDESThree congruent sides, (all the sides are equal)

9 in. 9 in.

9 in.

Classifying Triangles by their AnglesThere are three more types:AcuteObtuseRight

1. Acute TrianglesAcute Triangles have 3 acute angles

60°

60° 60° 60° 60° 60° 60°

2. OBTUSE TRIANGLESObtuse triangles have one obtuse (greater that 90 °) angle

110°

30° 40°

3. RIGHT TRIANGLESRight Triangles have one right angle (90°)

45°

90° 45°

Now…let’s practice what we have learned….What type of triangle has three congruent sides?A. Isosceles TriangleB. Equilateral TriangleC. Scalene Triangle

What type of triangle has one 90° angle and two acute angles?

A. Acute triangleB. Obtuse triangleC. Right Triangle

Classify the following according to sides and angles: and then check your work with the ruler and protractor

Scalene, right triangle

Classification #2 Check your answer with the ruler and protractor.

Equilateral, acute triangle

Classify the following and check with a ruler and protractor.

Isosceles, right triangle

Classify the following by both sides and angles:

Equilateral, acute triangle