How To Find The Radius

The radius of a circle is the distance from its center to any point on the circle. The value pi (?) establishes the relationship between a circle's circumference and its radius, and is the same for all circles. You can therefore find the radius of a circle from its circumference with your accuracy being limited to the accuracy of the value of pi that you use.

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Step 1

Select the value of pi that you'll use. Many math problems involving pi simply use the variable "pi" in the answer. The value 3.141593 is usually a more than an adequate estimation for high school math problems where a specific value of pi is required.

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Step 2

Learn the definition of pi. Pi is defined as Pi = c/d, where c is the circumference of a circle and d is its diameter. The diameter is the length of a line segment that contains the center of the circle and has points on the circle as its end points. A circle's circumference is always twice that of its radius.

Step 3

Substitute radius for diameter in the equation Pi = c/d. Since d = 2r for all circles, you can say that Pi = c/2r.

Step 4

Solve for r. The equation Pi = c/2r means that Pi (r) = c/2, so r = c / (2 Pi). The radius of a circle is therefore equal to c / (2 Pi) where c is the circumference of the circle.

Cite This Article

MLA

Robinson, Allan. "How To Find The Radius" sciencing.com, https://www.sciencing.com/radius-5617114/. 7 November 2009.

APA

Robinson, Allan. (2009, November 7). How To Find The Radius. sciencing.com. Retrieved from https://www.sciencing.com/radius-5617114/

Chicago

Robinson, Allan. How To Find The Radius last modified August 30, 2022. https://www.sciencing.com/radius-5617114/

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