if a line, line segment, or ray is perpendicular to a plane, it is perpendicular to every line, line segment, or ray in the plane that intersects it.
b. if a line is perpendicular to a plane, then any line perpendicular to the given line at the point of intersection with the given plane is in the given plane. if line a is perpendicular to plane p and line m at point x , what must also be true?