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)