Circles:
A circle is a plane curve that is equidistant from the center, as shown in Figure. The length of the perimeter of a circle is known as the circumference. A radius (r) of a circle is a line segment which joins the center of a circle with any point on its circumference. The diameter (D) of a circle is a line segment connecting two points of the circle through the center. The area of a circle is computed using the following formula:
![601_Circles.png](https://www.expertsmind.com/CMSImages/601_Circles.png)
A = πr2
The circumference which is given above of a circle is computed using the subsequent formula:
C = 2πr
or
C = D
Pi (π) is a theoretical number, approximately 22/7/3.141592654, representing the ratio of the circumference to the diameter of a circle. The scientific calculator makes this simple by designating a key for determining.
An area of a circle is always expressed in square units, and the perimeter of a circle is always expressed in the original units.