1. Classifying Triangles
by Angles and Sides
Geometry

2. Today’s Standard and EQ:
M4G1. Students will define and identify the characteristics of geometric figures through examination and construction.
a. Examine & compare angles in order to classify & identify triangles by their angles.
EQ: In what ways can triangles be classified?

3. Today we will be learning how to classify triangles according to length of sides and measurement of the angles.

4. First we will learn to classify by the
ANGLES

5. Right triangles have ONE right angle

6. Acute Triangles have three acute angles

7. Obtuse Triangles have ONE obtuse angle

8. Now You Try! Look at each triangle and decide if it is a
RIGHT, ACUTE, or OBTUSE triangle. 2 1 6 4 3 5

9. We will now learn to classify triangles by their sides.

10. Equilateral Triangles have 3 equal sides
If you collapsed all of the sides they would form a line.

11. Isosceles Triangles have 2 equal sides.

12. Scalene Triangles have
NO equal sides

13. Now You Try! 2 1 6 4 3 5 Look at each triangle and decide if it is an
EQUILATERAL, SCALENE or ISOCELES triangle. 2 1 6 4 3 5

14. Every triangle can be classified in two ways!
Remember…
Every triangle can be classified in two ways!
Measure of the Angles
Length of the Sides
Right triangles have one right angle
Equilateral triangles have three equal sides
Acute triangles have three acute angles
Isosceles triangles have two equal sides
Obtuse triangles have one obtuse angle
Scalene triangles have NO equal sides

15. You have now learned that triangles can be classified by either their sides or their angles.