The determination and properties of perpendicularity are as follows: if a line is perpendicular to both intersecting lines in a plane, then the line is perpendicular to the plane. If a line is perpendicular to a plane, then the line is perpendicular to all lines in the plane. Through a point in space, one and only one line is perpendicular to a known plane. EXTENDED INFORMATION The `determination and properties of line-plane perpendicularity are as follows: if a line is perpendicular to both intersecting lines in a plane, then the line is perpendicular to that plane. If a line is perpendicular to a plane, then the line is perpendicular to all lines in the plane. Through a point in space, there is and only one line perpendicular to the known plane.