sector(redirected from sectorial)
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(1) A sector in the plane is a region bounded by two rays issuing from an interior point of a figure and by an arc of its boundary cut off by these rays. In particular, a sector of a circle is bounded by two radii and an arc cut off by the radii. The area of a sector of a circle is equal to lr/2 or πr2α /360, where l is the length of the arc, α is the central angle (in degrees) subtended by the arc, and r is the radius of the circle.
(2) A sector in space is the part of a solid bounded by a conical surface whose vertex is in the solid and by the part of the solid’s surface cut off by the conical surface. A spherical sector is an example of a sector in space.