点或直线在平面上的射影位置是立体几何中的基本问题 ,许多立体几何问题往往都需要归结为确定点或直线在平面上的射影 .确定点或直线在平面上的射影没有一个统一的方法 ,主要是根据有关的定理或结论 .下面是几个常用的结论 .1 两平面垂直时 ,一个平面内的点在另一个平面上的射 The projective position of a point or line on a plane is a basic problem in three-dimensional geometry. Many three-dimensional geometric problems often need to be attributed to determining the projection of a point or line on the plane. There is no uniform method for determining the projection of a point or line on a plane. , mainly based on related theorems or conclusions. The following are several commonly used conclusions. 1 When two planes are vertical, the points in one plane are shot in another plane.