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Circle is the most important geometrical figure. A circle is defined as the locus of a point that is equidistant from a fixed point. In other words, circle is the set of all points that lie at same distance from a point.

The diagram of circle is shown below:

There are many terminologies that are associated with circle. Few important ones are as follows:

  • Center : The fixed point inside the circle, from where each point on circle is at equal distance, is known as center. It is denoted by "O" in above figure.
  • Radius : The distance from center to any point lying on the circle is called radius of the circle. Radius for a circle is fixed. It is generally denoted by "r".
  • Diameter : The diameter of a circle is line passing through center and meeting in circle on both sides. Diameter is shown in the above figure.
  • Circumference : Circumference is referred to the boundary of the circle.
Formulas Related to Circle:
There are few formulas that are related to circle and are very useful while performing different calculations with regard to circle.

1) Diameter of a Circle: Diameter of a circle is given by the following formula
Diameter = 2 x Radius
If diameter is denoted by "d" and radius by "r", then
d = 2 r

2) Radius of a Circle:
Radius of a circle can be calculated by the above formula as
r = $\frac{d}{2}$

3) Circumference of a Circle: The formula of circumference is
Circumference = 2 $\pi$ r

4) Area of a Circle:
Area of a circle is calculated as
Area = $\pi  r^{2}$

Related Calculators
Circle Calculator Circumference a Circle
Area Calculator Circle Chord of a Circle Calculator

More topics in  Circle
Parts of a Circle Circumference of a Circle
Radius of a Circle Diameter of a Circle
Area of a Circle Chord of a Circle
Secant of a Circle Tangent of a Circle
Center of a Circle Arc of a Circle
Sector of a Circle Segment of a Circle
Semicircle Unit Circle
Inscribed Angle of a Circle Polygon Inscribed in a Circle
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