直线垂直于平面.需要注意判定定理的条件中,“平面内的两条相交直线”是关键性词语,若两条直线不相交(平行),则直线与平面不一定垂直.要判定一条直线与一个平面垂直,只需要在该平面内找出两条相交直线与已知直线垂直.判定定理是由线线垂直,即证明直线与平面内的两条相交直线都垂直. Straight line perpendicular to the plane. Need to pay attention to the conditions of the decision theorem, “two intersecting lines in the plane ” is the key word, if the two lines do not intersect (parallel), the line and the plane may not be vertical. The straight line is perpendicular to a plane and only needs to find two intersecting straight lines perpendicular to the known straight line in the plane. The judgment theorem is perpendicular to the line, that is, the two intersecting lines in the straight line and the plane are perpendicular.