Circle in a Geometric Plane
Two-dimensional figure consisting of the set of all the points that are equally distant from the same point called the centre of the circle.
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In this figure :
- the point O is the centre of the circle,
- [latex]\overline{\textrm{OE}}[/latex] is a radius of the circle,
- [latex]\overline{\textrm{AD}}[/latex] is a diameter of the circle,
- [latex]\overline{\textrm{FG}}[/latex] is a chord of the circle,
- [latex]\overline{\textrm{TD}}[/latex] is tangent to the circle at point D.
Notation
Common notations for the circle are d for the diameter, r for the radius and C for the circumference. The letter O refers to the centre of the circle.Formulas
The formulas used to calculate the circumference C and the area A of a circle are the following :- [latex]C = 2π r[/latex]
- [latex]A = πr^2[/latex] or [latex]A = \dfrac{πd^2}{4}[/latex]