Triangles

A triangle is a polygon with three sides.

Triangles can be classified by side length or by angle measure.

Classification by Side Length
Equilateral Triangle	All sides congruent
Isosceles Triangle	At least two sides congruent
Scalene Triangle	No sides congruent

Classification by Angle Measure
Acute Triangle	All interior angles measure less than 90°
Right Triangle	Exactly one interior angle measures 90°
Obtuse Triangle	Exactly one interior angle measures more than 90°