Content

• Steps
• Advice
• Warning
• Necessary tools

When it comes to geometry, everyone thinks about comparing and distinguishing shapes, lines and angles. Triangles can be classified according to two different factors. And a triangle can be named for the corners or sides of the shape, or for both. With these triangles classification guidelines below, you can name each triangle yourself.

Steps

Method 1 of 2: Sort a Triangle by Edge

1. 

   Use the ruler to measure the three sides of the triangle.

2. 

   
   
   Place the ruler along one side and measure from this end of the edge to the point where the opposite side intersects.

3. 

   Record the measurements of each side.

4. 

   
   
   Compare the lengths of the sides together. Check which edge is longer or which edge is equal.

5. 

   Classify a triangle based on its 3-sided length comparison.
   • If a triangle has at least 2 sides of equal length it is classified as an isosceles triangle.
   • If the triangle has 3 sides with equal length, it is called an equilateral triangle.
   • If a triangle has no equal sides, it's an ordinary triangle.
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Method 2 of 2: Sort a Triangle by Angle

1. 

   
   
   Use a degree ruler to measure the 3 angles of the given triangle.

2. 

   Record the degree measurements for each angle.
   • The sum of the three angles of a triangle will always be 180 degrees.

3. 

   Use the measurements to classify right, obtuse or acute angles.

4. 

   Classify triangles according to measure and angle type.
   • It is an obtuse triangle if it has any angle greater than 90 degrees. In a prison triangle there will only be 1 single prison angle.
   • If the triangle has a 90 degree right angle, it is called a right triangle. The right triangle also has only one right angle.
   • An acute triangle is a triangle with 3 angles with measurements less than 90 degrees.
   • If a triangle has 3 equal sharp angles, this is an equilateral triangle. In an equilateral triangle, all three angles measure 60 degrees, because the sum of the three inner angles of a triangle is always 180 degrees.
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Advice

• An equilateral triangle can also be classified as an isosceles triangle, because it has at least two sides of equal measure.

Warning

• Triangles and right triangles both have sharp angles. However, these two types of triangles cannot be classified as an acute triangle, because an acute triangle must have 3 equal angles.
• When measuring the sides and angles of a triangle, always use a ruler, not estimated with the naked eye. Because the straight segments or the visible angles are equal, they can actually be deviated. If the measurement of the edge and angle is wrong, this will affect the classification of the triangle.

Necessary tools

• Ruler
• Measure