三垂线定理是立体几何中的重要定理,它是证明直线和直线垂直的有力工具,在研究空间图形的计算问题(如点线距离与二面角的计算等)时,也常要借助三垂线定理给出合理的依据．因此,正确理解并掌握三垂线定理,对学好立体几何有着重要意义． The vertical theorem is an important theorem in solid geometry. It is a powerful tool that proves that a straight line is perpendicular to a straight line. When studying the computational problems of spatial graphics (such as point-line distance and dihedral angle calculation, etc.), it often uses three. The vertical line theorem gives a reasonable basis. Therefore, a correct understanding and mastery of the three-perpendicular theorem is of great significance for the study of solid geometry.