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

In the same plane, there is and is only one straight line perpendicular to the known straight line through a point. Vertical will always appear 90°. Of all the line segments connecting a point outside the straight line to every point on the straight line, the perpendicular segment is the shortest. Simply put: the vertical line segment is the shortest.

The distance from the point to the straight line: The length of the perpendicular segment from a point outside the straight line to the straight line is called the distance from the point to the straight line.

Extended information:

When the datum is a straight line and the line being evaluated is a straight line, the perpendicularity is the two points that are perpendicular to the datum line and farthest apart and include the straight line being measured. The distance between planes; when the datum is a straight line and the plane being evaluated is a plane, perpendicularity is the distance between the two farthest planes that are perpendicular to the datum line and contain points on the plane being measured.

According to the determination theorem of plane perpendicularity, to prove that two planes are perpendicular to each other, just find a straight line in one plane that is perpendicular to the other plane.

Baidu Encyclopedia - Vertical