What Does a Circle Mean?

Features

• A line is a set of points, and for a set of points to be deemed a circle, every point must be equidistant from the exact center.

Pi

• Dividing any circle's circumference by its diameter results in an unending number 3.14159, commonly shortened to 3.14. This is π (pi)--the ratio of circumference to diameter.

Radius and Diameter

• The radius (r) of a circle is the distance (D) from any point of the circle to its center. Its diameter is the distance between opposite points of a circle. Because radius is half of the diameter, diameter can be found by the formula D = 2r.

Area

• While the area (A) of a line cannot be measured, the space contained within those lines can be measured, which is considered the area of a circle. The formula for area depends on whether one knows the radius or diameter. In the case of radius the formula is A =  πr², while if diameter is known, the area is A = π/4 x D².

Circumference

• The distance around a circle (circumference) is determined by several formulas depending on what information is given. If the radius is known, it is C = 2πr. For diameter it is C = πD. Knowing the area, the circumference is the square root of 4πA.