Circles

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Video

A circle is defined as a plane curve set an equidistant from a midpoint. A line from the midpoint any point on the circle is called the radius. If a line segment touches to parts of the circle, it is called a chord. A chord directly through the middle of the circle is called the diameter.

The entire length of the circle is referred to as the circumference.

In order to determine the circumference of a circle, you must use a formula. You need to be familiar with some definitions.

You are going to have to remember that pi is equal to 3.14.

Diameter (d)

Diameter is the distance from one edge of the circle, through the middle, to the opposite side of the circle.

Radius (r)

Radius is defined as ½ of the diameter, or the distance from the mid-point of a circle to its outer edge.

Formula for Calculating Circumference

The information you are given in a question will dictate the formula you should use to calculate the circumference. If you are given the radius, calculate the diameter by multiplying by two. Dividing the diameter by two will give you the radius.