Classify triangles

Key Notes:

In an acute triangle, all three angles are less than 90°.
In a right triangle, one angle is exactly 90°.
In an obtuse triangle, one angle is greater than 90°.

Learn with an example

A triangle has angle measurements of 88°, 90° and 2°. What kind of triangle is it?

  • acute
  • right
  • obtuse

This triangle is a right triangle. The 90° angle is a right angle.

A triangle has angle measurements of 60°, 60°, and 60°. Is this triangle equilateral?

  • yes
  • no

This triangle is equilateral. All 3 angles are equal.

Is this triangle scalene?

  • yes
  • no

Look at this triangle:

This triangle is not scalene. All 3 sides are the same length.

let’s practice!