Key Concepts: Classifying Triangles

Classifying by Sides

• Scalene Triangle: No sides are congruent.
• Isosceles Triangle: At least two sides are congruent.
• Equilateral Triangle: All three sides are congruent.

Classifying by Angles

• Acute Triangle: All angles are less than 90°.
• Right Triangle: One Angle is exactly 90°.
• Obtuse Triangle: One Angle is greater than 90°.
• Equiangular Triangle: All angles are equal (each is 60°).

Key Facts

• Every Equilateral Triangle is also equiangular (and vice versa).
• An Isosceles Triangle has a vertex Angle (between the congruent sides) and two base angles (which are congruent).