CHAPTER
9
Geometry
9.1 Perimeter
9.2 Area
9.3 Circles
9.4 Volume
9.5 Angles and Triangles
9.6 Square Roots and the Pythagorean Theorem
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Slide 2
9.1
Perimeter
OBJECTIVES
a Find the perimeter of a polygon.
b Solve applied problems involving perimeter.
Copyright 2011 Pearson Education, Inc.
Slide 3
9.1
Perimeter
Perimeter of a Polygon
A polygon is a closed geometric figure with three or
more sides. The perimeter of a polygon is the
distance around it, or the sum of the lengths of its
sides.
Copyright 2011 Pearson Education, Inc.
Slide 4
9.1
Perimeter
a Find the perimeter of a polygon.
EXAMPLE A Find the perimeter of this polygon.
9m
Solution
5m
4m
Add the lengths of all sides.
8m
Perimeter = 5 m + 4 m + 6 m + 8 m + 9 m
= (5 + 4 + 6 + 8 + 9) m
= 32 m
Copyright 2011 Pearson Education, Inc.
6m
Slide 5
9.1
Perimeter
Perimeter of a Rectangle
A rectangle is a polygon with four sides and four 90
degree angles.
The perimeter of a rectangle is twice the sum of
the length and the width, or 2 times the length plus
2 times the width.
l
P = 2l + 2w, or P = 2 (l + w).
w
w
l
Copyright 2011 Pearson Education, Inc.
Slide 6
9.1
Perimeter
a Find the perimeter of a polygon.
EXAMPLE B Find the perimeter of a barn door that is 10
f by 12 f.
Solution
P = 2l + 2w
= 212 f + 210 f
= (212) f + (210) f
= 24 f + 20 f
= 44 f
Copyright 2011 Pearson Education, Inc.
Slide 7
9.1
Perimeter
Perimeter of a Square
A square is a rectangle in which all sides have the
same length.
The perimeter of a square is four times the length
s
of a side.
P = 4s
s
s
s
Copyright 2011 Pearson Education, Inc.
Slide 8
9.1
Perimeter
a Find the perimeter of a polygon.
EXAMPLE C Find the perimeter of a square garden with
sides of length 15 feet.
Solution
P = 4s
= 4 ∙ 15 f
= 60 f
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