What is the area of a circle if its circumferece is a?

Expert Answers
hala718 eNotes educator| Certified Educator

Given that a circumference of a circle is a.

We need to find the area of the circle as a function of a.

==> We know that:

C= 2*pi * r = a

==> r= a/2pi ..............(1)

Now we will determine the area of a circle formula.

==> A = r^2 * pi

But r= a/2pi

==> A = (a/2pi)^2 * pi

==> A = (a^2/4pi^2 * pi

==> A = (a^2/4pi )

Then the area of the circle is (a^2/4pi) square units.

justaguide eNotes educator| Certified Educator

The circumference of a circle with radius r is 2*pi*r and the area of the circle is pi*r^2

For a circle with circumference a

2*pi*r = a

=> r = a / 2*pi

The area of the circle is pi*(a / 2*pi)^2

=> pi*a^2/4*pi^2

=> a^2/4*pi

The area of the circle is a^2/4*pi square units