Transcript three or more line segments

Polygons
Introduction
Irma Crespo 2010
What is a polygon?
A polygon is a simple closed
figure in a plane formed by
three or more line segments.
A Polygon
closed figure
bounded by straight
line segments
Which are the polygons?
Polygons
close figures; formed by
straight line segments
Non-polygons
open figures; formed by
curves or lines
Polygons are grouped
by the number of sides.
Name of Polygon
Number of Sides
Triangle
3
Quadrilateral
4
Pentagon
5
Hexagon
6
Heptagon
7
Octagon
8
Nonagon
9
Decagon
10
Undecagon
11
Dodecagon
12
n-gon
n
What is the fewest number of
sides a polygon can have? 3
What is the largest number of
sides a polygon can have? n
Polygons are either
convex or concave.
Convex: line segments
connecting any two
points on the shape lie
entirely inside the
shape
Concave: some line
segments connecting
any two points on the
shape pass outside the
shape
Quickies
Parallel lines are
lines that are across
each other but
never meet.
90° angles: L-shape,
no matter how you
turn it.
Quadrilateral Family Tree
Quadrilateral
(4 sides)
Trapezoid
Parallelogram
(one pair of parallel sides)
(two pairs of parallel sides)
Rhombus
Rectangle
(all side lengths are equal)
(four 90° angles)
Square
(all side lengths are equal
and four 90° angles)
Summary
A polygon is a simple closed figure in a plane formed
by three or more line segments.
Polygons are grouped based on the number of sides.
Polygons are either convex or concave.
Quadrilaterals are polygons of four sides.
Exit Slip
Complete the family tree on the Activity
Sheet, “Roots of a Square.”
Don’t forget to write your name, date, and
hour.
This is an extra credit point towards
homework or quiz.
Turn it in before leaving class.
Practice Worksheet
Complete the practice worksheet.
Work with a partner or on your own.
Submit completed worksheet for grading.
Solutions are discussed the next day.
Main Resources
http://www.absorblearning.com/mathematics/demo/u
nits
Larson, Boswell, and Stiff. Geometry. 2001. Illinois:
McDougall Littell.
PowerPoint created by Irma Crespo.
University of Michigan-Dearborn, School of
Education. Winter 2010.