Triangle Facts for Kids

For other uses, see Triangle (disambiguation).

A triangle is a basic shape with three straight sides. It also has three corners, which are called vertices. The three angles inside any triangle always add up to 180 degrees. It's the simplest type of polygon, which is a shape made of straight lines. When we talk about a triangle with corners named A, B, and C, we write it as $\triangle ABC$ .

Types of Triangles
- Triangles by Side Length
- Triangles by Angle Size
How Triangles Are Used
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Types of Triangles

This is an isosceles right triangle. It has a right angle and two sides that are the same length.

We can sort triangles into different groups based on their sides or their angles.

Triangles by Side Length

If all three sides of a triangle are the exact same length, it's called an equilateral triangle.
If a triangle has two sides that are the same length, it's an isosceles triangle.
If all three sides of a triangle have different lengths, it's a scalene triangle.

Triangles by Angle Size

If a triangle has a right angle (an angle that measures exactly 90 degrees), it's a right triangle. The side opposite the right angle is called the hypotenuse.
If one of a triangle's angles is larger than 90 degrees, it's an obtuse triangle.
If all three angles in a triangle are smaller than 90 degrees, it's an acute triangle.

Equilateral triangle
Isosceles triangle
Scalene triangle
Right triangle
Obtuse triangle
Acute triangle

How Triangles Are Used

Triangles are super useful in many areas! The study of how triangles work, especially their angles and sides, is called trigonometry. This field is very important in things like engineering, physics, and even video game design.

Modern computers often use triangles to build more complicated images and shapes. For example, when you see a 3D character or object in a video game, it's actually made up of thousands of tiny triangles!