求直线与平面所成的角是学习立体几何中线面关系的重点,我们必须熟练地掌握它．在求直线与平面所成的角时,应注意先判断直线与平面的位置关系．当直线与平面斜交时,关键是确定斜线上某点在直线或平面上的射影．最常用的方法就是利用面面垂直的性质定理,即寻找一个经过这点且与已知平面垂直的平面,作出它们的交线,再由这点向交线作垂 Finding the angle between a straight line and a plane is the key to studying the line-plane relationship in solid geometry. We must master it skillfully. When calculating the angle between the straight line and the plane, it should be noted that the positional relationship between the straight line and the plane is first determined. When the straight line is skewed with the plane, the key is to determine the projection of a point on the line or plane on the slope. The most common method is to use the surface vertical property theorem, that is, to find a plane passing through this point and perpendicular to the known plane, make their intersection, and then from this point to the intersection