1. Triangles
Grade 4

2. Triangles
You have learned to classify different types of polygons. Today, you will learn to classify triangles.
How are triangles different from other polygons?
Watch video on Triangles (and take notes)

3. Math Vocabulary
There are two important ways to sort triangles. You can look at the lengths of their sides. You can also look at the sizes of their angles.

4. Classify by SIDES What is meant by congruent sides?
Congruent sides = sides that are the same length.
Equilateral triangle = 3 congruent sides
Isosceles triangle = 2 congruent sides
Scalene triangle = NO congruent side

5. Classify by ANGLES Triangles can be classified by angles.
A right triangle has one right angle
An acute triangle has three acute angles. All of its angles measure less than a right angle.

6. Classify by Angles
An obtuse angle has one obtuse angle. One angle has a measure greater than a right angle.

7. Practice
Classify this triangle by its sides and then by its angles.

8. Practice - Answer Scalene; Acute
Classify this triangle by its sides and then by its angles.
Scalene; Acute

9. Practice
Classify this triangle by its sides and then by its angles.

10. Practice - Answer
Classify this triangle by its sides and then by its angles.
Right; Isosceles

11. Homework
Pg. 204 (#1 – 20)