Area of a circle is ,
is the radius of the circle.
is the ratio of the circumference of a circle to its diameter.
The perimeter of a circle is the distance covered by going around its boundary once. The perimeter of a circle has a special name: Circumference, which is times the diameter which is given by the formula
A circular segment is a region of a circle which is “cut off” from the rest of the circle by a secant or a chord.
The angle of a sector is that angle which is enclosed between the two radii of the sector.
The length of the arc of a sector can be found by using the expression for the circumference of a circle and the angle of the sector, using the following formula:
Where is the angle of sector and is the radius of the circle.