如何计算Circle

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A circle is the set of all points in a plane that are exactly the same distance (the radius) from a central point. All four measurements — radius, diameter, circumference, and area — can be calculated from just one known value using the mathematical constant π (pi ≈ 3.14159).

分步指南

1. 1Radius (r): the distance from the centre to any point on the circle
2. 2Diameter (d): twice the radius — d = 2r
3. 3Circumference (C): the perimeter of the circle — C = 2πr = πd
4. 4Area (A): the space enclosed — A = πr²

例题解析