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The passage discusses examples of geometry problems involving quadrilaterals, circles, and their properties. Quadrilaterals examples include finding the area of a parallelogram and the difference between two trapezoids. Circle examples include finding areas bounded by concentric circles and regions within or bounded by circles.

Examples of problems involving quadrilaterals include finding the area of a parallelogram with given dimensions, and finding the area of the difference between two isosceles trapezoids.

Examples of problems involving circles include finding the area between two concentric circles with given radii, finding the area of a triangle inscribed in a circle, and finding the area of a square inscribed in a circle.

Quadrilaterals

Example 1. A city block is in the form of a parallelogram whose shorter


diagonal AB is perpendicular to side BC, as shown in the figure. The
shorter sides represent streets and the longer sides represent avenues. If
the distance between the avenues is 400ft and the length of each street is
500 ft, find the area of the block.
Quadrilaterals
2 2
500 400 DC =
400
500 300
2000
3
AB
AB
=
=
( ) ( )
2000
500 333333.33 . 37037.04 . .
3
BC AB sq ft or sq yd
| |
= =
|
\ .
Quadrilaterals
Example 2. Find the area of the rectilinear figure shown, if it is the
difference between two isosceles trapezoids whose corresponding sides
are parallel.
Quadrilaterals
( )
3
8 6
3 6
2.25
8
z
z
=
= =
( )( ) ( ) ( ) ( ) ( ) ( )
1 1
12 18 8 18 2 2.25 2.136 18 2 2.136 6 51.132
2 2
A sqin
(
= + + + =

2 2
3 8 73 y = + =
8 2
73
2 73
2.136
8
x
x
=
= =
Circles
Area = x radius
2
= /4 x diameter
2
2
1 1
2 2
A RC R u = =
2 2
4
A r D
t
t = =
2 C R D t t = =
Circumference = 2 x radius = x diameter
Area = 1/2 x radius
x
arc
Area = Area of sector Area of triangle
1 1
2 2
A RC ba =
Sector of a circle:
Segment of a circle:
Circle
Example 1. The section of a certain solid is bounded by two concentric
circles whose radii are 6.1 ft and 4.1 ft. Find the area of this section.
( )
( )
( ) ( ) ( ) ( )
( )( ) ( )( )
2
1
2
2
2 2 2 2
1 2
6.1
4.1
6.1 4.1 6.1 4.1
6.1 4.1 6.1 4.1 10.2 2 64.089
A
A
A A
sq ft
t
t
t t t
t t
=
=
(
= =

= + = =
Circles
Example 2. A triangle is inscribed in a circle of radius 6 inches as
shown in the diagram. What is the area of the shaded polygon?
( )( )
1 1
5 12 30
2 2
A bh in = = =
If a triangle is inscribed in a circle with the
diameter as one side, it will always be a
right triangle.
Circles
Example 3. A square is inscribed in a circle of 10 .What is the area of the
shaded region?
10
10
P C d
d
t t = = =
=
2 2 2
2
2
10
2 100
50
7.07
x x
x
x
x units
+ =
=
=
~
( )
( )
2
2
2
2
2
7.07 50
5 25
25 50 28.5
square
circle
circle square
A x
A r
A A unit
t t t
t
= = =
= = =
= ~
Circles
Example 4. Find the perimeter and area enclosed by the track ABCDEF in the
figure?
( )( ) ( ) ( )
2 440 2 2 70 440 2 1319.82 Total Perimeter r ft t t = + = + =
( ) ( )( )
2
2
70 440 70 2 76993.804 Total Area r bh sq ft t t = + = + =
Circles
Example 5. Each of the four circles shown in the figure is tangent to the other
three. If the radius of each smaller circle is a = 2.71, find the area of the
largest circles.
Circles
2.71
sin60
3.13
3.13 2.71 3.31 5.84
x
x
radius a
=
=
= + = + =
( )
2
2
5.84 107.14 A r squnit t t = = =
Circles
Example 6. The plane area shown consists of an isosceles trapezoid (non-
parallel sides equal) and a segment of a circle. If non-parallel sides are
tangent to the segment at points A and B, find the area of the composite
figure.
Circles
3 2
cos60
3"
R
R
=
=
sin60
3
2.598"
3 2.598 0.40"
h h
R
h
R h
= =
=
= =
( ) ( ) ( )( )
2
2
1 1 1 1
3 60 3 2.598
2 2 2 180 2
4.712 3.897 0.815"
segment of acircle
segment of acircle
A R ab
A
t
u
(
| |
= =
|
(
\ .

= =
Circles
4.6
tan30
7.967"
x
x
=
=
( ) ( )( )
1 1
3 18.934 4.6 50.45
2 2
trapezoid
A a b h = + = + =
( )
3 2 3 2 7.967 18.934" x + = + =
0.815 50.45 51.265"
total
A = + =

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