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Triangles: Classification

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 °