Classifications of Triangles
A right triangle has one 90° angle and a variety of often-studied topics:
The Equilateral triangleshown on the left has three congruent sides and three congruent angles.
Each angle is 60°.
The Isosceles triangle shown on the left has two equal sides and two equal angles.
The Scalene Triangle has no congruent sides. In other words, each side must have a different length.
The Acute Triangle has three acute angles (an acute angle measures less than 90°).
The Obtuse Triangle has an obtuse angle (an obtuse angle has more than 90°). In the picture on the left, the shaded angle is the obtuse angle that distinguishes this triangle.
Since the total degrees in any triangle is 180°, an obtuse triangle can only have one angle that measures more than 90°.