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The area of a circle is the number of square units it covers. If a circle has radius \(r\) units, its area is \(\pi r^2\) square units.
For example, a circle has radius of 3 inches. Its area is \(\pi 3^2\), or \(9\pi\), square inches. This is about 28.3 square inches.
A circle is made of all the points that are the same distance from a given point. That given point is the center of the circle.
Every point on this circle is 5 cm away from point \(A\).
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There is a proportional relationship between the diameter and circumference of any circle. The constant of proportionality is pi. The symbol for pi is \(\pi\).
This relationship can be represented with the equation \(C=\pi d\), where \(C\) represents the circumference and \(d\) represents the diameter. In the graph, pi can be seen as the value of \(C\) when the value of \(d\) is 1.
Some approximations for \(\pi\) are \(\frac{22}{7}\), 3.14, and 3.14159.