Head First 2D Geometry

T

he three fi

elds

ar

e diff

er

ent

s

hapes and sizes.

triangle properties

First we need to pick a venue

There are three local fields where this sort of event can take place,

and your choice of venue is absolutely critical. It determines how

many people can come to your festival and what it will cost to

make sure they all pay to get in.

Here are the three possible venues:

Field A

Field B

Field C

What do you need to find out about each potential venue to

figure out the following? Just describe these in normal words—

don’t worry about geometry jargon.

a) The fencing costs:

b) The capacity:

We don’t w

ant p

eople

coming in for f

r

ee!

T

he number of p

eople who

can come to the f

es

tiv

a

l

you are here 4 151

P as in P

er

imeter

T

hese line nota

tions mean the

length of the line segment

bet

ween those points.

W

ork

s f

or w

eird shapes, t

oo!

permeter is the total length of sides

What do you need to find out about each potential venue to

figure out the following? Just describe these in normal words—

don’t worry about geometry jargon.

a) The fencing costs:

b) The capacity

we don’t w

ant p

eople

coming in for f

r

ee!

number of p

eople who can

come t

o the f

es

tiv

a

l

The length of the edges

The area—how much space there is

If y

ou wrote “p

er

imeter,” tha

t’s

corr

ec

t, t

oo.

The perimeter is the total length of the sides of a shape

If you add up the lengths of all of the sides, or edges, of a

shape then you’ve got the perimeter. The exact calculation you

need to do depends on how many sides your shape has.

A

P = AB + BC + CA

B C

B

D

C

J

I

P = AB + BC + CD + DE + EF

A

E

+ FG + GH + HI + IJ + JA

F

G

H

152 Chapter 4