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The sum of the measures of the interior angles of a triangle is 180 degrees.

Since all the sides of equilateral triangles are the same length, all the angles are the same...

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The interior angles of an equilateral triangle are all 60 degrees.

What about a square?

That's easy! By definition, all the interior angles of a square are right angles -- That means that they are all 90 degrees.

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What about other regular polygons?

To figure out the measure of the interior angles of a regular pentagon, hexagon, heptagon, etc, we need more than just a protractor! What if we needed to find the interior angle of a regular polygon with 100 sides? That might be a little difficult to draw!

 

Here are two methods to find the measure of the interior angles of a regular polygon:

For both methods, we will use the fact that the sum of the measures of the interior angles of a triangle is 180 degrees!