Miriam has taught middle- and high-school math for over 10 years and has a master's degree in Curriculum and Instruction.
Learn the definition of the diameter of a circle and how to find it using a simple formula. See some examples, then test your knowledge with a short quiz.
The diameter of a circle is a segment whose endpoints lie on the circle and whose midpoint is the center of the circle. When someone says 'lie on the circle,' that means on the outline that traces the circle, not the space within that outline. The center of the circle is a point exactly in the middle of the space within the outline. The center is also the same distance away from every point on the outline of the circle. The distance from the center to a point on the circle is called a radius.
The segment AB is a diameter. Point C is the center of the circle, and it is also the midpoint of segment AB. Segments AC and CB are of equal length and are each half the length of the diameter. AC and CB are each a radius of the circle. A radius of a circle is a segment with one endpoint on the circle and the other endpoint at the center of the circle.
There is only one diameter drawn on circle C. However, every circle has an infinite number of possible diameters. Imagine you have to cut a round cookie into two equal pieces. No matter how you turn the cookie, as long as you make one straight cut right through the center point of the cookie, you will split it along a diameter.
The formula to find the diameter states the relationship between the diameter and the radius. The diameter is made up of two segments that are each a radius. Therefore, the formula is: Diameter = 2 * the measurement of the radius. You can abbreviate this formula as d=2r.
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There are segments DA and CB shown on this circle. DA is a radius, since it has one endpoint at the center of the circle and the other on the circle. DA has a length of 3.5 cm. CB is a diameter, since it has both endpoints on the circle and passes through the center of the circle. The diameter equals two times the radius, so the diameter of this circle is 7 cm, since 2 * 3.5 is equal to 7.
The diameter of a circle is a segment whose endpoints lie on the circle and whose midpoint is the center of the circle. The distance from the center to a point on the circle is called a radius. Every circle has an infinite number of possible diameters. The formula for finding the diameter of a circle is two times the radius (2 * radius).
The diameter stretches from one side of a circle to the other with its midpoint at the center of the circle.
To calculate the diameter, multiply the length of the radius of the circle by 2.
As a consequence of having explored this lesson, you could subseqently have the ability to:
Write the formula for finding the diameter of a circle and also abbreviate it
Recognize the meaning of the diameter, center and radius of a circle
Use what you've learned to calculate the diameter of a circle
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