求斜线与平面所成的角,关键是过斜线上一点作平面的垂线.而这条垂线往往是由两个平面垂直的性质定理提供的.这样我们作线面角时,可先找证或作一个平面垂直于已知平面,然后在垂面内过垂面和斜线的交点作两个垂面的交线的垂线,再把垂足和斜足连结起来,线面角就作出来了.下面举例说明. To find the angle between the slash and the plane, the key is to use a point on the overslope as a perpendicular line to the plane. This vertical line is often provided by the property theorem of the two planes. When we make the line angle, we can To find out or make a plane perpendicular to the known plane, then use the intersection of the vertical and oblique lines in the vertical plane as the vertical line of the intersection of the two vertical planes, and then connect the vertical foot and the oblique foot. The horn is made. Here is an example.