The Acute Triangle
An acute triangle has three acute angles. An acute angle is an angle that measures less
than 90 degrees; so, in an acute triangle, each angle has a measure of less than 90 degrees. Equilateral
triangles are always acute angles. In an equilateral triangle, like the picture above-right, all
angles measure 60 degrees. There are also acute triangles that are not equilateral triangles, like the
one pictured above-left.
The Obtuse Triangle
The Right Triangle
Back to Triangle Introduction
Classification by Angle Measure
Classification by Length of Sides
Northern Michigan University
Beth Roberts: broberts@nmu.edu