Definition:Circle

Definition



 * Circle.png

Also see

 * Definition:Segment of Circle
 * Definition:Sector


 * Area of Circle: the area of a circle is $\pi r^2$, where $r$ is its radius.
 * Perimeter of Circle: the perimeter of a circle is $2 \pi r$, where $r$ is its radius.


 * Equation of Circle: the equation of a circle of radius $R$ whose center is at the origin:
 * in Cartesian coordinates is $x^2 + y^2 = R^2$
 * in polar coordinates is $\map r \theta = R$
 * parametrically can be expressed as $x = R \cos t, y = R \sin t$.