Decision method 1. When a straight line is perpendicular to a plane, it is perpendicular to any straight line on the plane, which is called line-plane verticality for short.
2. If the shadow of a straight line on the three vertical theorem plane is perpendicular to a diagonal line on the intersection plane, the straight line is perpendicular to the diagonal line.
Property ① In the same plane, there is one and only one straight line perpendicular to the known straight line. Must be 90 degrees vertical.
② Of all the line segments connecting a point outside the straight line with a point on the straight line, the vertical line segment is the shortest. Simply put: the vertical line segment is the shortest.
③ Distance from point to straight line: The length from a point outside the straight line to the vertical section of this straight line is called the distance from point to straight line.
Line-plane verticality condition 1) If a straight line is perpendicular to two non-parallel lines in a plane, the straight line is perpendicular to the plane.
2) If two nonparallel perpendicular lines of a straight line are parallel to the plane, the straight line is perpendicular to the plane.
3) If both surfaces A and B are perpendicular to the C plane, the intersection line of the two surfaces A and B is also perpendicular to the C plane.
4) If the straight line is perpendicular to the B plane parallel to the A plane, the straight line is perpendicular to the A plane.
5) If the projections of any point on a straight line on the plane coincide, the straight line is perpendicular to the plane.
6) The distance from any point on a straight line to the plane is equal to the distance from the point to the intersection of the straight line and the plane, so the straight line is perpendicular to the plane.
The above is the judgment method and nature of line verticality for reference!