5-1 Classifying Triangles

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

First we will learn to classify by the

ANGLES

Right triangles have ONE right angle

Acute Triangles have three acute angles

Smaller than 90o

Smaller than 90o

Smaller than 90o

Acute Angle

Obtuse Triangles have ONE obtuse angle

Obtuse Angle

We will now learn to classify triangles by their sides.

If you collapsed all of the sides they would form a line.

Equilateral Triangles have 3 equal sides

Isosceles Triangles have 2 equal sides.

Scalene Triangles have NO equal sides.

Classifying  Triangles  by  Their  Sides  §  EQUILATERAL  –  3  congruent  sides  

 

§  ISOSCELES  –  at  least  two  sides    

 congruent  

 

§  SCALENE  –  no  sides  congruent  

EQUILATERAL

ISOSCELES

SCALENE

1-3A

Slide 3 of 3

1-3B

Slide 3 of 3

1-3C

Slide 3 of 3

1-3D

Slide 3 of 3

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

10-1 ANGLES OF A TRIANGLE

1-1A

Slide 1 of 2

1-2A

Slide 2 of 2

1-2B

Slide 2 of 2

1-2C

Slide 2 of 2

1-2D

Slide 2 of 2

1-2D

Slide 2 of 2

1-2E

Slide 2 of 2

1-2E

Slide 2 of 2

1-2F

Slide 2 of 2

1-2G

Slide 2 of 2

1-2H

Slide 2 of 2

1-2I

Slide 2 of 2

1-2J

Slide 2 of 2

1-2J

Slide 2 of 2

GUIDED PRACTICE for Examples 3 and 4

5 .

Find the measures of the acute angles of the right triangle in the diagram shown.

26° and 64° ANSWER

The perimeter of a triangle is 29 cm. The length of the first side is twice the length of the second side. The length of the third side is 5 more than the length of the second side. Find the side lengths and then classify the triangle by its side lengths.

The ratio of angle measures of a triangle is 7:16:22. Find the angle measures and then classify the triangle by its angle measures.