Circle Area and Circumference

Date: 03/16/2002 at 19:21:22
From: Briddy 
Subject: Area and Circumference

I need help with area and circumference. Are radius and diameter the 
same thing as area and circumference?

Date: 03/17/2002 at 11:18:14
From: Doctor Sarah
Subject: Re: Area and Circumference

Hi Briddy - thanks for writing to Dr. Math.

The circumference of a circle is the distance around it. It is 
measured in linear units (inches, feet, etc.). The formula for the 
circumference of a circle is:

   C = pi*d (pi times the diameter)

The diameter of a circle is a chord that passes through the center of 
the circle. (A chord is a line segment with endpoints on the 
circumference of a circle.) 

The area of the circle is the number of square units needed to cover 
its surface. It is measured in square inches, square feet, etc. The 
formula for the area of a circle is:

   A = pi * r^2 (pi times the radius squared)

The radius of a circle is a line segment with one endpoint at the 
center of the circle and the other endpoint on the circumference of 
the circle. It is exactly half the diameter of the circle.

Does this help?

- Doctor Sarah, The Math Forum
  http://mathforum.org/dr.math/