(1) The property that a line is perpendicular to a plane: If a line is perpendicular to a plane, it is perpendicular to all the lines in the plane.

Vertical lines and planes

(1) Determination of line-plane verticality: If a line is perpendicular to two intersecting lines in a plane, it is perpendicular to the plane.

(2) Plane parallelism: If two planes are parallel, a straight line is perpendicular to one plane and the other plane.

(3) the nature of the vertical surface; If two planes are perpendicular, a straight line intersecting vertically in one plane is perpendicular to the other plane.

Surface vertical

(1) Definition: If the dihedral angle formed by two planes is a straight dihedral angle, then the two planes are vertical.

(2) Determination of vertical plane: If a plane passes through the vertical line of another plane, it is perpendicular to this plane.