Classification of Triangles and Angles

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Angles and Triangles

All triangles have three sides. They can be categoried according to their internal angles.
All triangles have three sides. They can be categoried according to their internal angles. Ray Massey, Getty Images

 

Geometry involves the understanding of geometric language. When you're studying geometry it's important to learn the properties of figures. This gallery classifies angles and types of triangles and lists the key properties of each figure, along with illustrations.

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Acute Angle

Acute Angle
Acute Angle Acute Angle.

An acute angle measures less than 90 degrees.

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Obtuse Angle

Obtuse Angle
Obtuse Angle.

An obtuse angle measures greater than 90 degrees but less than 180 degrees.

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Reflex Angle

Reflex Angle
Reflex Angle.

A reflex angle measures between 180 and 360 degrees.

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Right Angle

Right Angle
Right Angle.

A right angle measures exactly 90 degrees. (Remembering the uppercase letter L will help you remember the angle of a right angle)

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Straight Angle

Straight Angle
Straight Angle.

Straight angles measure exactly 180 degrees.

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Acute Triangle

Acute Triangle
Acute Triangle.

All angles are acute in an acute triangle.

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Equilateral

Equilateral
Equilateral.

Equilateral triangles have three equal sides.

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Isosceles Triangle

Isosceles Triangle
Isosceles Triangle.

Isosceles triangles have two sides that are equal in length.

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Obtuse Triangle

Obtuse Triangle
Obtuse Triangle.

Obtuse triangles have one angle that is obtuse.

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Right Triangle

Right Triangle
Right Triangle.

Right triangles have one right angle.

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Scalene Triangle

Scalene Triangle
Scalene Triangle.

Scalene triangles have 3 sides that are all different lengths.

Edited by Anne Marie Helmenstine, Ph.D.

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Your Citation
Russell, Deb. "Classification of Triangles and Angles." ThoughtCo, Mar. 13, 2017, thoughtco.com/classification-of-triangles-and-angles-4071215. Russell, Deb. (2017, March 13). Classification of Triangles and Angles. Retrieved from https://www.thoughtco.com/classification-of-triangles-and-angles-4071215 Russell, Deb. "Classification of Triangles and Angles." ThoughtCo. https://www.thoughtco.com/classification-of-triangles-and-angles-4071215 (accessed November 21, 2017).