Triangle Types and Classifications: Isosceles, Equilateral, Obtuse, Acute and Scalene

Classifications of Triangles

Right Triangles

A right triangle has one 90° and a variety of often-studied properties including:

The Equilateral triangle shown on the left has three equal sides and three equal angles.

Each angle is 60°

The Isosceles triangle shown on the left has two equal sides and two equal angles.

The Scalene Triangle has no congruent sides. In other words, each side must have a different length..

The Acute Triangle has three acute angles (an acute angle measures less than 90°)

The Obtuse Triangle has an obtuse angle (an obtuse angle has more than 90°). In the picture on the left, the shaded angle is the obtuse angle that distinguishes this triangle

Since the total degrees in any triangle is 180°, an obtuse triangle can only have one angle that measures more than 90°.

Practice Problems

What kind of triangle is pictured on the left?

Triangle Type

What kind of triangle is pictured on the left?

Triangle Type

What type of triangle is pictured on the left?

Answer

Classify the triangle on the left

Answer

Classify the triangle on the lef

Answer

Types of Triangles

Isosceles, Equilateral, Scalene, Obtuse. . .