Circumference of a circle: This is the length of the line that marks out the circle. We can also call it perimeter of the circle.

Circumference where Radius of the circle.

*(Note: Area of a circle )*

A Circular Ring: This is the object that is bound by the circumference of two concentric circles of different radius.

If the radius of the outer ring is R and the radius of the inner ring is r, then the

Area of the ring

Semi-circle: If the circle is divided into two equal halves, then we will we will get two semi-circle.

Length if the arc (half the circumference of the circle)

Perimeter of the semi-circle

Quadrant: If a circle is divided into four equal parts by two mutually perpendicular diameters, the part so obtained is called a quadrant.

(one fourth of the circumference of the circle)