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Polygons and Symmetry. Goals: Define a Polygon Define and Use reflectional symmetry and rotational symmetry Define regular polygon and use the central angle theorem of a regular polygon. Examples. Not Polygons. Polygons. Vocab.
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Polygons and Symmetry Goals: Define a Polygon Define and Use reflectional symmetry and rotational symmetry Define regular polygon and use the central angle theorem of a regular polygon
Examples Not Polygons Polygons
Vocab A closed plane figure formed by three or more segments such that each intersect exactly two other segments. Segments of a polygon The common endpoints of those segments
All angles congruent All sides are congruent Both equiangular and equilateral An angle whose vertex is the center of the polygon and whose sides pass through two consecutive vertices
Reflectional Symmetry: A figure has reflectional symmetry if and only if its reflected image across a line coincides exactly with the preimage, the original figure. Axis of Symmetry: A line that divides a figure into two congruent reflected halves.
Rotational Symmetry: A figure has rotational symmetry if and only if it has at least one rotation image not counting rotation images of 0º or multiples of 360º, that coincide with the original figure.
Activity with Patty Paper… The measure of a central angle of a regular polygon with n sides is given by the following formula: ___________________________
Example 1: Find the measure of the central angle of each regular polygon below: a) decagon b) heptagon c) 15-gon Measure of central angle: Measure of central angle: Measure of central angle: