VERSION 2. Parallel Lines and Planes. By:. B R C. Reading Geometry. Read the symbol || as is parallel to . Arrowheads are often used in figures to indicate parallel lines.
Read the symbol || as is parallel to.
Arrowheads are often used in figures to indicate parallel lines.
In geometry, two lines in a plane that are always the same distance apart are parallel lines. No two parallel lines intersect, no matter how far you extend them.
Two lines are parallel if and only if they are in the same plane and do not intersect.
AB || CD
AB || CD
BA || DC
Planes can also be parallel. The shelves in a bookcase are examples of parts of planes. The shelves are the same distance apart at all points, and do not appear to intersect. They are parallel. In geometry, planes that do not intersect are called parallel planes.
Sometimes, lines that do not intersect are not in the same plane. These lines are called skewlines.
Two lines that are not in the same plane are skew if and only if they do not intersect.