A sector of a circle is an area enclosed by two radii and an arc.
In the figure above, θ is the central angle and r are the radii of the circle.
(Central angle is the angle subtended at the center of the circle)
(Arc length is the length along the curved line making an arc)
The smaller area is known as the minor sector and the larger part is known as the major sector.
Special Sectors
A semicircle (half of a circle) is a sector with central angle of 180°.
A quadrant (quarter of a circle) is a sector with central angle 90°.
A sextant has a central angle of 60°.
An octant has a central angle of 45°.
