11.2 Perimeter and 11.2 Perimeter and CircumferenceCircumference

Presented by Lynn BeckPresented by Lynn Beck

11 in

32 in

Radius

Diameter

The Perimeter of a PolygonThe Perimeter of a Polygon Perimeter is one of the most basic measures of Perimeter is one of the most basic measures of

geometry. Ex.: Length of a fence around your geometry. Ex.: Length of a fence around your house, state border lengthhouse, state border length

Definition: The PERIMETER of a polygon is the Definition: The PERIMETER of a polygon is the distance around it.distance around it.

To find the perimeter, we add the lengths of To find the perimeter, we add the lengths of its sides. NOTE: PERIMETERS ARE its sides. NOTE: PERIMETERS ARE MEASURED IN LINEAR UNITS, SUCH AS FEET MEASURED IN LINEAR UNITS, SUCH AS FEET OR METERS.OR METERS.

We can also use a We can also use a FORMULAFORMULA to find the to find the perimeter of some polygons. perimeter of some polygons.

Formula of a Triangle Formula of a Triangle P P == a+b+c a+b+c Perimeter equals the sum of the three Perimeter equals the sum of the three

sidessides

a

b

c

ExampleExample

b=20cm

a=12cm

c=24cmP = 12+20+21

= 56 or 56cm

Formula for perimeter of a Formula for perimeter of a rectanglerectangle

Perimeter is equal to two times the length plus Perimeter is equal to two times the length plus two times the width of a rectangle.two times the width of a rectangle.

wlP 22 l

w

ExampleExample

Perimeter of a rectanglePerimeter of a rectangle

3 in

7 in

inor

wlP

3030

1020

5*210*2

22

CIRCUMFERENCECIRCUMFERENCE Definition: The distance around a circle is called its Definition: The distance around a circle is called its

CIRCUMFERENCE.CIRCUMFERENCE. d d is the diameter, is the diameter, r r is the radius, and is is the radius, and is

approximately 3.14 approximately 3.14 oror

r 2 C or dC

d

7

22

ExampleExample

cmor

dC

12.2512.25

)8(14.3

8 cm

Composite FiguresComposite Figures

Two or more basic Two or more basic figures may be figures may be combined to form a combined to form a COMPOSITE COMPOSITE FIGURE.FIGURE.

5 ft

7 ft

ftP

P

C

C

d

dC

total 281711

17557

112

227

22

7

The End!The End!

Lynn Beck represented Perimeter and Lynn Beck represented Perimeter and Circumference Circumference

Of Polygons