Triangles

A triangle is a shape with three sides and three corners. It is one of the simplest shapes in geometry. Triangles come in many forms, but they all have three sides. The three angles inside any triangle always add up to 180 degrees.

Types of Triangles

Triangles are grouped by their sides or angles. An equilateral triangle has three equal sides. An isosceles triangle has two equal sides. A scalene triangle has no equal sides. A right triangle has one 90 degree angle, like the corner of a book.

The giant pyramids at Giza show huge triangle shapes.
The giant pyramids at Giza show huge triangle shapes. (Ricardo Liberato / Wikimedia Commons)

Triangles Everywhere

Triangles are very strong shapes. That is why they are used in bridges, roofs, and towers. You can see triangles in pizza slices, sailboats, and road signs. The pyramids in Egypt are built using triangle shapes. Triangles help hold up big buildings because they do not bend easily.

Fun Facts

  • A triangle is the strongest shape for building because it cannot be pushed out of shape.
  • The word triangle means three angles.
  • The Bermuda Triangle is a famous area in the ocean shaped like a triangle.

Did You Know?

Every three-sided shape on a flat surface is a triangle, no matter how big or small.