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# 4.3 - Polygons

Author: Kyle Webb
##### Description:
• Classify and name polygons based upon the number of sides
• Define Concave and Convex Polygons
• Define Regular Polygons and find measure of interior angles
• Find Exterior angles and their measures

Polygons were introduced in the first unit, and in this section we will learn more about how to classify polygons as well as how to find measures of angles in polygons.

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Tutorial

## Types of Angles Acute Angle is an angle that is less than 90°

Right Angle is an angle that is 90° exactly

Obtuse Angle is an angle that is greater than 90° but less than 180°

Straight Angle is an angle that is 180° exactly

Reflex Angle is an angle that is greater than 180°

This is a great tool to illustrate how to classify various angles: http://bit.ly/vIySAB

## Concave and Convex Polygons

Introducing and contrasting Convex and Concave Polygons.

Source: MICDS Integrated Mathematics 1 Notes, Geogebra

## Polygon Names

The table below reviews the list of names for polygons with different numbers of sides Source: MICDS Integrated Mathematics 1 Notes

## Regular Polygons

Defining and illustrating regular polygons.

Source: MICDS Integrated Mathematics 1 Notes, Geogebra

## Sum of Interior Angles

Can you find the sum of the measures of angles (if you added all the angles together) within a given polygon?

Using the pattern you notice below, determine a rule to find the sum of the measures of the interior angles of an n-gon. Be sure to consider the number of sides (n) and the number of possible diagonals within the polygon.

Source: MICDS Integrated Mathematics 1 Notes

## Exterior Angles

Source: MICDS Integrated Mathematics 1 Notes, Geogebra

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