Question

Find the radius of a circle which has a sector area of 9 pi whose central angle is 90 degrees.

Answer 1

The area is A= 3/2π

Explanation:

The area of whole circle is:

A

c

=

π

×

r

2

=

9

π

The central angle

60

o

is

1

6

of a full angle, so the area of the sector is:

A

s

=

1

6

A

c

=

1

6

×

9

π

=

9

6

π

=

3

2

π

Answer 2

Answer:360/90 = 4

Total area = 4 times that of the sector.

Explanation:

A 90 deg sector has 1/4 the area of the circle.

Total circle area = 4*9pi = 36pi