Areas Related to Circles
Perimeter of a Circle The distance around a circle is called its perimeter or usually called its circumference. The ratio of circumference of a circle to its diameter is constant and it is denoted by the Greek letter . Circumference = π × diameter = 2πr, where r is the radius of the circle. For practical purposes, we generally use π = 22/7 or 3.14 approximately Area of a circle The area of a circle = × r2, where r is the radius of the circle and is a constant. It can be verified by cutting a circle into a number of sectors and rearranging them into a nearly rectangle. Area of sector A sector is a part of a circular region enclosed by two radii and the corresponding arc. A sector of a circle is called a major sector if its corresponding arc is the major arc of the circle. A sector of a circle is called a minor sector if its corresponding arc is minor arc of the circle. Length of an arc of a Sector Segment of a circle A segment is a part of the circular region enclosed between a chord and the corresponding arc. If the boundary of a segment has a major arc of a circle, then the segment is called a major segment. If the boundary of a segment has a minor arc of a circle, then the segment is called a minor segment. Area of segment of a circle Areas of Combinations of Plane Figures Areas of combinations of plane figures are calculated by adding or subtracting the areas of individual figures involved.