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Triangles! The Types of Triangles and How to Classify Them

Updated on December 6, 2012
Triangles! | Source

Triangle Basics

A triangle has several key components.

A triangle always has three sides, the sides are connected and create the shape.

A triangle is a polygon ( a multi sided figure).

A triangle has three angles. These angles always add to make 180° (degrees).

Three Classified Triangles by Sides
Three Classified Triangles by Sides | Source

Classified by the Triangles Sides

When classifying the triangle by it's sides there are three choices. In order to figure out if a triangle is classified by one of these methods it is important to note that the sides can be measured with a ruler or the figure may have has marks to show that two sides are equal.

Equilateral - meaning that all three sides have the exact same measure.

Isosceles - two side are equal with a third side being a different measure

Scalene - all three sides have different measures

Triangles by angles
Triangles by angles | Source

Classifying Triangles by their Angles.

Another method of classifying triangles is by their angles. In order to determine the classification you would need to measure the angles with a protractor in order to determine the angles measure. Arcs within a figure also mark whether two angles of congruent.

Acute - all of the angles in the triangle are less than 90°.

Right- There is exactly one right (90°) angle in the triangle. There could never be more than one because it could not form a triangle with two right angles and only three sides.

Obtuse - The triangle has one angles that is greater than 90°


Important to note that a triangles can be classified in one way or in both ways. I can say that a triangle is both equilateral and acute because it describes two different things about the triangle.


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    • kthix10 profile image

      kthix10 5 years ago from IL

      Thanks!! Now if anyone knows a school that needs a math teacher in the chicagoland area for next year ....

    • YvetteParker profile image

      YvetteParker 5 years ago from AUGUSTA, GA

      Kthix10, you have created another useful resource for mathematics students and teachers alike. Your article is concise, easy to understand, and very visual! In other words: short, sweet, and to the point! Voted up!