If a line is perpendicular to each of two intersecting lines
at their point of intersection, then the line is
perpendicular to the plane determined by them. 
Through a given point there
passes one and only one plane perpendicular to a given line.

Through a given point there
passes one and only one line perpendicular to a given plane.

Two lines perpendicular to
the same plane are coplanar.

Two planes are
perpendicular to each other if and only if one plane
contains a line perpendicular to the second plane. 
If a line is perpendicular
to a plane, then any line perpendicular to the given line at
its point of intersection with the given plane is in the
given plane.

If a line is perpendicular
to a plane, then every plane containing the line is
perpendicular to the given plane.

If a plane intersects two
parallel planes, then the intersection is two parallel
lines.

If two planes are
perpendicular to the same line, they are parallel.

