- Acute Triangle: three acute angles
- Equiangular Triangle: three congruent acute angles
- Right Triangle: one right angle
- Obtuse Triangle - one obtuse angle
Holt Geometry Book
The definition of a triangle is a polygon that is three-sided.
Here are their classifications by their side lengths:
- Equilateral Triangle: three congruent sides
- Isosceles Triangle: at least two congruent sides
- Scalene Triangle: no congruent sides
Holt Geometry Book
