The
area
of
a
____________________
with
radius
r
=
1
unit
is
?
units^2
.
(
Remember
that
?
?
3
.
1415926
.
.
.
)
Since
all
circles
are
____________________
,
their
areas
increase
by
a
square
of
the
linear
scale
(
zoom
)
factor
.
That
is
,
a
circle
with
radius
6
has
an
area
that
is
36
times
the
area
of
a
circle
with
radius
1
.
Thus
,
a
circle
with
radius
6
has
an
area
of
36
?
units^2
,
and
a
circle
with
radius
r
has
area
A
=
?
r^2
units^2
.
Area
=
?
r^2
____________________
=
2
?
r
=
?
d
The
circumference
of
a
circle
is
its
____________________
.
It
is
the
distance
around
a
circle
.
The
circumference
of
a
circle
with
radius
r
=
1
unit
is
2
?
units
.
Since
the
perimeter
ratio
is
equal
to
the
ratio
of
similarity
,
a
circle
with
radius
r
has
circumference
C
=
2
?
r
units
.
Since
the
diameter
of
a
circle
is
twice
its
radius
,
____________________
way
to
calculate
the
circumference
is
C
=
?
d
units
.
A
part
of
a
circle
is
called
an
arc
.
This
____________________
a
set
of
points
a
fixed
distance
from
a
center
and
is
defined
by
a
central
angle
.
____________________
a
circle
does
not
include
its
interior
region
,
an
arc
is
like
the
edge
of
a
crust
of
a
slice
of
pizza
.
A
region
that
resembles
a
slice
of
pizza
is
called
a
sector
.
It
is
formed
by
two
radii
of
a
central
angle
and
the
arc
between
their
endpoints
on
the
circle
.
