If a straight line is perpendicular to any two non-parallel lines, it is perpendicular to a plane. Method: Make a straight line A on a given plane, make a vertical line B of the straight line A from a given point (set as X), and the intersection point is Y. On the plane, point Y is the vertical line C of the straight line A, and then point X is the vertical line D of the straight line C, which intersects with point Z, so the straight line D is the vertical line from the specified point to the specified plane. It is proved that because straight line A is perpendicular to B and A is perpendicular to C, A is perpendicular to the plane XYZ where B and C are located, thus it is deduced that A is perpendicular to D .. and straight line D is perpendicular to C and D is perpendicular to A, so D is perpendicular to the plane where A and C are located, that is, the designated plane.