section 1.6. in geometry, a figure that lies in a plane is called a plane figure. a polygon is a...
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![Page 1: Section 1.6. In geometry, a figure that lies in a plane is called a plane figure. A polygon is a closed plane figure with the following properties. Identifying](https://reader036.vdocument.in/reader036/viewer/2022072006/56649f435503460f94c63e2e/html5/thumbnails/1.jpg)
Section 1.6
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In geometry, a figure that lies in a plane is called a plane figure. A polygon is a closed plane figure with the following properties.
Identifying Polygons
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Properties of Polygons
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1. It is formed by three or more line segments called sides.
2. Each side intersects exactly two sides, one at each endpoint, so that not two sides with a common endpoint are collinear.
Each endpoint of a side is a vertex of the polygon.
The plural of a vertex is vertices.
A polygon can be named by listing the vertices in consecutive order.
For example, ABCDE and CDEAB are
both correct for the polygon at the right.
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A polygon is convex if no line that contains a side of the polygon contains a point in the interior of the polygon.
A polygon that is not convex is called nonconvex or concave.
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Tell whether the figure is a polygon. If it is not, explain why not. If it is a polygon, tell whether it is convex or concave.
a.
It is not a polygon, since some segments intersect more than two segments.
Example 1
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b.
Is a polygon and it is convex.
c.
It is a polygon and it is concave.
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A polygon is named by the number of sides.
Classifying Polygons
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Number of Sides Type of Polygon3 Triangle4 Quadrilateral5 Pentagon6 Hexagon7 Heptagon8 Octagon9 Nonagon
10 Decagon12 Dodecagonn n-gon
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The term n-gon, where n is the number of a polygon sides, can also be used to name a polygon.
For example, a polygon with 14 sides is a 14-gon.
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In an equilateral polygon, all sides are congruent.
In an equiangular polygon, all angles are congruent.
A regular polygon is a convex polygon that is both equilateral and equiangular.
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Classify the polygon by the number of sides. Tell whether the polygon is equilateral, equiangular, or regular.
The polygon is an octagon.
It is a regular polygon.
Example 2
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Given an equilateral hexagon. Find the length of each side.
4x + 3 = 5x – 1
x = 4
side = 4(4) + 3 = 19 mm
Example 3