在立体几何问题中,正方体和正棱锥常会作为考查线面关系的载体出现,若能熟知这类几何体中线面垂直关系,则会对解题起到事半功倍的效果.以上图中正三棱锥S-ABC为例(确定顶点在底面的射影为底面的中心和点在侧面的射影),O为底面△ABC的中心,D为BC的中点,连结AD、SD, In the three-dimensional geometry problem, the cube and the regular pyramid as a carrier to examine the relationship between the surface, if we can familiarize the vertical relationship of such geometry in the plane, it will play a multiplier effect .In the figure is a regular triangular pyramid S-ABC Example (determine the vertex projection on the bottom surface as the center of the bottom surface and on the side of the point projection), O is the center of the bottom △ ABC, D is the midpoint of BC, connecting AD, SD,