Triangles are a different type depending on how many sides are the same length (which is also how many angles are equal).
Triangles are equilateral, isosceles or scalene depending on whether 3, 2 or 0 side lengths and angles are equal.
Here is an interactive game to help you learn about the types of triangle.
Click on a triangle so it drops into the correct "bucket."
In total, there are 10 triangles to clear.
If a triangle drops into the wrong "bucket," you will lose one of your three lives.
Good luck!
Type of Triangle by Angles
Triangles are a different type depending on the size of the angles inside the triangle.
Triangles are acute, obtuse or right triangles depending on whether all angles are acute (less than 90°), one angle is obtuse (more than 90°) or one angle is a right angle (90°).
Acute Triangles
Acute triangles have all acute angles (less than 90°).
3 angles are less than 90°.
Obtuse Triangles
Obtuse triangles have one angle that is obtuse (more than 90°, less than 180°).
1 angle is more than 90°.
2 angles are less than 90°.
Triangles can be classified by both lengths of sides and by angles. This means a triangle can be both acute and isosceles, or obtuse and scalene.
The slider below shows more real examples of the types of triangles.
Open the slider in a new tab
Interactive Widget
Here is an interactive widget to help you learn about the types of triangles.
What Is a Triangle?
A triangle is a 2-dimensional shape with three sides and three angles.
Indicating Equal Sides
If a triangle has sides of equal length, the equal sides are indicated by drawing a short line through the sides:
Indicating Equal Angles
Angles are indicated by drawing an arc between the sides.
Equal angles can be indicated by drawing the same number of arcs at each angle. The two angles with a two arcs are equal to each other:
The Interior Angles of a Triangle
The angles between the sides, that are inside the triangle, are called interior angles.