The surface figure can be seen as the track of moving line, formingcurved surfaceThe moving line of is called bus.For example, the front view of a cone is aan isosceles triangle, thistriangleThe waist isconea bus or bus bar.
A surface is a geometric figure. It is the track of a moving line (line or curve) moving continuously in space. The line (line or curve) that produces the surface is calleda bus or bus bar。The line or surface that controls the movement of the bus is called the conductor or guide surface. Any position of the bus on the curved surface is called the prime line, as shown in Figure 1. Curve AB is the conductor, straight line SB is the bus, and all positions of SB movement are prime lines.Busbar isstraight lineFormed whencurved surfaceThe center is calledRuled surface；Formed when the bus is curvedcurved surfacebe calledCurved surface。The surface formed when the generatrix moves regularly is calledruleSurface.Control bus movementspot、Line、noodlesbe calledfixed point、wirewayAnd guide surface.[1]
Figure 1
Bus bar of cylinder
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As shown in Figure 2, take the straight line on one side of the rectangle asRotation axis, the rotation body formed by the surface formed by the other three sides is calledcylinder。The axis of rotation is called the axis of the cylinder. The circular surface formed by rotation perpendicular to the axis is called the bottom of the cylinder. The surface formed by rotation parallel to the axis is called the side of the cylinder. No matter where the axis is rotated, the side parallel to the axis is called the cylindera bus or bus bar。
Figure 2
generating line
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The structural characteristics of a cone are the same as that of a cylinder. A cone can also be regarded as a plane figure.As shown in Figure 3, the rotating body enclosed by the straight line where one right side of a right triangle is located is calledcone, the hypotenuse of the triangle corresponds to thea bus or bus barFor example, SA and SB are both conical buses.
The frustum is a geometric body formed by rotating the right angled trapezoid 360 ° with its waist perpendicular to the bottom as the axis.
As shown in Figure 4, the upper and lower surfaces of the frustum are two circular surfaces, called the bottom surface of the frustum.The common vertical line between the two bottom surfaces is called the height of the frustum (as shown in Figure 4
)。The curved part is called the side of the frustum.The waist of a rotating right angled trapezoid that is not perpendicular to the bottom is called a frustuma bus or bus bar(in Figure 4
)。[2]
Figure 4
Cylindrical bus
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Make parallel lines through each point of a curve C in space, and these lines will form a cylinder.Curve C is called the directrix of the cylinder, and the parallel lines that form the cylinder are called the generatrix of the cylinder.
