If parallel lines lie in two distinct
planes, the planes must be
parallel.
FALSE
Three planes can intersect at
a point.
TRUE (ex: corner of
classroom)
Three planes can intersect at
a line.
TRUE
If two lines in space are not
parallel, then they must intersect.
FALSE (Skew lines)
If lines are perpendicular to the
same plane, they are parallel.
TRUE
If a line is perpendicular to a
line in a plane, then it is
perpendicular to the plane.
FALSE (Mailbox
problem… must be
perp. to two lines in
plane passing
through foot)
If a line is perpendicular to
one of two parallel planes,
then it is perpendicular to the
other.
TRUE
If a line is perpendicular to a
plane, then it is perpendicular
to all lines in the plane.
FALSE (Not perp. to
lines not passing
through its foot)
If separate planes contain skew
lines, the planes are parallel.
FALSE
Two planes can intersect at a
point.
FALSE (planes
continue infinitely)
Two planes can intersect at a
line.
TRUE (crack at top
of classroom)
The union of two planes is an
angle.
FALSE (an angle is
formed by lines – this
is called a dihedral
angle)
Two intersecting lines can lie in
more than one plane.
FALSE (intersecting
lines determine a
plane)
Two parallel lines determine a
plane.
TRUE
Two skew lines determine a plane.
FALSE (by definition,
skew lines lie in
different planes)
Three points determine a plane.
FALSE (must be
non-collinear)
If three lines are parallel, then they
must be coplanar.
FALSE
In a plane, if two lines are
perpendicular to the same line,
they are parallel.
TRUE
In space, if two lines are
perpendicular to the same line,
they are parallel.
FALSE