Bus is the conductor connecting the cut-off branch circuit in electrical equipment. It is the carrier for collecting and distributing electricity, also called bus bar. (This is practical use) In a conic curve, a generatrix is a line segment connecting the vertex and any point on the circumference of the bottom of the cone. (This is a mathematical definition) A sector is an important figure related to a circle, and its area is related to the central angle (vertex angle) and radius of the circle. The area of a sector with a central angle of n and a radius of r is n/360 π r 2. If the vertex angle is in radians, it can be simplified as 1/2× arc length× radius. (Arc length = radius × radian, and arc length = central angle (arc system) × radius) The sector is also similar to a triangle. The simplified area formula can also be regarded as: 1/2× arc length× radius, which is similar to the triangle area: 1/2× base× height. Sector area formula: s sector =(lR)/2 (l is the arc length of the sector) = 1/2 θ r 2 (θ is the central angle in radians) s sector = (n/360) π r 2 (n is the degree of the central angle and r is the radius of the base circle) Note: π is the pi, which is approximately equal to.