a sector of a circle is the portion of a disk enclosed by two radii and an arc, where the smaller area is known as the minor sector and the larger being the major sector. The area A of a circle with radius r is given by A = πr2. The circumference C of that same circle is given by C = 2πr. But these are the formulas for the entire circle. Sometimes you will need to work with just a portion of a circle's revolution, or with many revolutions of the circle.
