Triangles are those handy‐dandy three‐sided polygons with which mathematicians have done so much work, particularly the right triangle.

The most important thing to remember about all triangles is that the sum of their interior angles is 180°. Again, the sum of the interior angles of any triangle is 180°. Once more, the sum of the interior angles of any triangle is 180°!

example-triangles

Triangle Inequality

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Angles and Their Side Lengths

angles-and-their-side-lengths

Equilateral Triangle

equilateral-triangle

Isosceles Triangle

isoceles-triangle

Scalene Triangle

scalene-triangle

Right Triangle 

right-triangle

30° – 60° – 90° Triangle  30-60-90-triangle

45° – 45° – 90° Triangle

45-45-90-triangle

3 – 4 – 5 Triangle

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