How to Classify Triangles
Classify Triangles by SidesClassify a Triangle by Angles
Edited by Katy Linsao, Peter, Genius_knight, Kalpit and 6 others
Geometry often involves comparing and classifying shapes, line segments and angles. Triangles can be classified by 2 different attributes. A triangle may be named for its angles or for its lines. It may also be given a dual classification and classified by lines and angles. You will be able to give every triangle a more specific name after learning how to classify triangles.
EditSteps
EditMethod 1 of 2: Classify Triangles by Sides
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1Measure each side of the 3 sides of the triangle using a ruler.Ad -
2Place the ruler at the end of each line segment of the 3 lines in the triangle and measure to the opposite endpoint of each line. -
3Make note of the measurement for each of the 3 triangle sides. -
4Determine how the 3 sides compare in length. Inspect to see if some lines are longer than others in length and if any of the lines are equal in length. -
5Place the triangle into a category based on the comparison that you concluded about 3 line segment lengths of the shape.
- A triangle with at least 2 congruent, equal, sides falls into the category of isosceles.
- A triangle with all 3 congruent sides will be classified as equilateral.
- A triangle with no congruent sides is labeled as scalene.
- A triangle with at least 2 congruent, equal, sides falls into the category of isosceles.
EditMethod 2 of 2: Classify a Triangle by Angles
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1Use a protractor to measure each of the 3 interior angles of the given triangle. -
2Record the measurement of each angle in degrees.- The 3 angles inside a triangle will always have a sum of 180 degrees.
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3Distinguish if the angles are right, acute or obtuse according to their measurements. -
4Classify the triangle according to the measurement and the type of angles.
- Name the triangle as an obtuse triangle if any of the angles are greater than 90 degrees. An obtuse triangle will only have 1 obtuse angle.
- Classify the triangle as a right triangle if the triangle possess a right angle of 90 degrees. A right triangle will only have 1 right angle.
- Categorize the triangle as acute if all 3 of its angles are less than 90 degrees.
- Determine that the triangle is equiangular if all 3 of its angels, which would also have to be acute, are congruent. In an equiangular triangle, all 3 of the angles will be 60 degrees, because the sum of the 3 interior angles in a triangle is always 180 degrees.
Ad - Name the triangle as an obtuse triangle if any of the angles are greater than 90 degrees. An obtuse triangle will only have 1 obtuse angle.
EditTips
- An equilateral triangle can also be classified as an isosceles triangle, because at least 2 of its sides are congruent.
EditWarnings
- An obtuse triangle and a right triangle will both have acute angles. However, they can not be classified as acute. An acute triangle must have 3 acute angles.
- Always use a tool, not your naked eye, to measure the line segments and angles of a triangle. The lines or angles may appear congruent when, in fact, there is only a small difference among them. The error in measurement will change the classification.
EditThings You'll Need
- Ruler
- Protractor
EditRelated wikiHows
Article Info
Categories: Geometry
Recent edits by: Jakesoup, Acinzia, Lean
In other languages:
Português: Como Classificar Triângulos, Español: Cómo clasificar triángulos, 中文: 给三角形分类, Italiano: Come Classificare i Triangoli, Deutsch: Dreiecke klassifizieren, Français: Comment classifier les triangles
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