Page 99 - Math Course 1 (Book 2)

Polygons

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Key Concept Polygon

Words A polygon is a closed f gure formed by a f nite number of coplanar segments such that

(1) the sides that have a common endpoint are noncollinear, and
(2) each side intersects exactly two other sides, but only at their endpoints.

Symbol
A polygon is named by the letters of its vertices, written in alphabetical order.
Example Nonexample
L M
A Z J K B A

H E C F
X Y D E G H J K N O
B C W G F

The perimeter P of a polygon is the sum of the length of the sides of the polygon.
The circumference C of a circle is the distance around the circle.
Words
The area A is the number of a square units needed to cover a surface.

Examples triangle square rectangle circle

Perimeter/ P = b + c + d P = 4s P = 2l + 2w C = 2πr
Circumference

Area 1
A = bh A = s 2 A = lw A = πr 2
2
S

c d r
h w
S S

b
S l

Let’s Begin

Identify Polygons
There are 4 sides, so this is a quadrilateral.
Examples No line containing any of the sides will pass
through the interior of the quadrilateral, so it is
convex.
A. Name the polygon by its number of sides.
Then classify it as convex or concave, regular The sides are not congruent, so it is irregular.
or irregular.

quadrilateral, convex,
Answer
irregular

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