Download Section 1.6 - Mrs. Lawhon

Section 1.6
Classify Polygons
(p. 42)
Objectives
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Students will learn how to classify polygons.
Identifying Polygons
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In geometry a figure that lies in a plane is called a plane figure.
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A polygon is a closed plane figure with the following properties:
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Formed by 3 or more line segments called sides.
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Each side intersects exactly two sides.
Each endpoint of a side is a vertex of the polygon.
Naming a Polygon
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A polygon is named by it vertices which are listed in consecutive order.
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Pentagon ABCDE, Pentagon BCDEA, Pentagon EDCBA, ...
Classify Polygons
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If the sides of a polygon were made into lines, and the lines never passed
through the interior of the polygon, then the polygon is convex.
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If the lines do pass through the interior, then the polygon is concave.
Examples
Classify Polygons by Sides
Classify Polygons by Sides
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A polygon whose sides are all congruent is called equilateral.
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A polygon whose angles are all congruent is called equiangular.
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A convex polygon that is both equilateral and equiangular is a regular
polygon.
Examples
Classify the polygon by the number of sides. Tell whether the polygon is
equilateral, equiangular, or regular. Explain your reasoning.
Example
The expressions (9x+5)° and (11x-25)° represent the measures of two angles
of a regular nonagon. Find the measure of an angle of the nonagon.
Homework
p. 44 - 45
3 - 17 odd, 18 - 23 all, 29