Draw a vertical line from a point on a straight line to the plane to get the vertical foot, and then connect the vertical foot with the intersection of the straight line and the plane. The included angle between the connecting line and the original straight line is the line-plane angle.

In the same plane, there is one and only one straight line perpendicular to the known straight line. Must be 90 degrees vertical. Of all the line segments connecting points outside the straight line and points on the straight line, the vertical line segment is the shortest. Simply put: the vertical line is the shortest.

Distance from point to straight line: The length from a point outside a straight line to the vertical section of this straight line is called the distance from point to straight line.

Extended data:

When the benchmark is a straight line and the evaluated line is a straight line, the verticality is the distance between the two farthest planes that are perpendicular to the benchmark straight line and contain points on the measured straight line; When the datum is a straight line and the measured plane is a plane, verticality is the distance between the two farthest planes perpendicular to the datum straight line and containing points on the measured plane.

According to the judging theorem of surface verticality, it is only necessary to find a straight line perpendicular to the other plane in order to prove that two planes are perpendicular to each other.

Baidu Encyclopedia-Vertical