In the simplest form of definition, sector of a circle is a pie shaped portion of the area of the circle. It is a region bound by two radii and an arc lying between two radii.
A sector of a circle :
Area of Circle Sector: (with central angle)
If the angle is in degrees, then area = (/360)x PI r2
If the angle is in radians, then area = ((/(2PI))x PI r2