Download Using Patterns and Inductive Reasoning

Name the polygons with the
following number of sides:
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•
•
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•
•
•
•
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3
4
5
6
7
8
9
10
12
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Triangle
Quadrilateral
Pentagon
Hexagon
Heptagon
Octagon
Nonagon
Decagon
Dodecagon
Polygons
Geometry
Mr. Zampetti
Unit 3, Day 2
Today’s Objectives
• To learn how to classify polygons
• To learn how to find the sum of the
measures of the interior and exterior angles
of a polygon
Definition
Polygon: a closed plane
figure with at least
three sides.
Video: Polygons in Architecture
Without the use of your notes:
Matching names with number of sides:
http://www.quia.com/cm/86645.html?AP
_rand=2098901149
Concentration game:
http://www.quia.com/jg/1507267.html
Definition
Convex: a polygon is
convex if no diagonal
contains points
outside the polygon.
http://img.sparknotes.com/figures/B/b333d91dce2882b2db48b8ad670cd15a/convexconcave.gif
Definition
Concave: a polygon is
concave if a diagonal
contains points
outside the polygon.
http://img.sparknotes.com/figures/B/b333d91dce2882b2db48b8ad670cd15a/convexconcave.gif
Theorem 2-3: Polygon Interior
Angle-Sum Theorem
The sum of the
measures of the
interior angles of an
n-gon is (n - 2)180.
Practice
• Find the sum of the measure of the interior angle
of the following polygons:
– 15-gon
– 20-gon
– Decagon
– Dodecagon
(n-2) x 180 video
• Cool Video!!
Theorem 2-4: Polygon Exterior
Angle-Sum Theorem
The sum of the
measures of the
exterior angles of a
polygon, one at each
vertex, is 360.
http://www.mathlove.com/new3/product/img/TTA05/5.jpg
Video: General Definitions of
Polygons
Definition
Equilateral polygon: a
polygon with all sides
congruent.
Equiangular polygon: a
polygon with all angles
congruent.
Regular polygon: a polygon
that is both equilateral and
equiangular.
Homework
Work Packet:
Polygons