Types of Triangles by Sides

Triangles can also be classified by the lengths of their sides. Learning this helps students identify patterns and understand how different triangles relate to each other.

In this post, we’ll explain the main types of triangles based on sides and provide simple examples for elementary students.

What Is a Triangle?

A triangle is a polygon with three sides and three angles. All triangles are closed shapes with straight sides.

Equilateral Triangles

An equilateral triangle has all three sides equal.

• All angles are also equal (each 60°)
• Looks perfectly balanced and symmetrical

Isosceles Triangles

An isosceles triangle has two sides equal.

• The angles opposite the equal sides are also equal
• Often seen in bridges and rooftops

Scalene Triangles

A scalene triangle has no sides equal.

• All angles are different
• Looks irregular compared to equilateral or isosceles triangles

Step-by-Step: How to Identify a Triangle by Sides

• Step 1: Measure or compare the lengths of each side.
• Step 2: Determine the type of triangle:
  • All sides equal = equilateral
  • Two sides equal = isosceles
  • No sides equal = scalene
• Step 3: Optionally, check the angles for more information about the triangle.

Common Student Mistakes

• Confusing isosceles with equilateral
• Not measuring sides carefully
• Assuming scalene triangles are “wrong” because they look irregular

Using a Triangles by Sides Flip Book

A triangles by sides flip book helps students remember the different types of triangles and their attributes. Keeping it in an interactive math notebook gives students an easy reference during geometry lessons. T

Raven's Thoughts

Classifying triangles by sides gives students a deeper understanding of geometry. Step-by-step identification and visual examples make learning triangle types engaging and easy to remember.