有一圆锥形的屋面层如图1,虚线AB为一梁与圆锥的截交线,并且截平面与圆锥轴线平行。根据投影原理.截交线的正投影面反映双曲线的实际形状(图2)。根据双曲线的标准方程式 There is a conical roof layer as shown in Fig. 1. The dotted line AB is the intersection of a beam and a cone, and the section plane is parallel to the axis of the cone. According to the principle of projection, the orthogonal projection plane of the cut line reflects the actual shape of the hyperbola (Figure 2). Standard equation based on hyperbola