Anti-parallel straight lines
From Encyclopedia of Mathematics
with respect to two given lines 
and 
Two straight lines 
and 
which intersect 
and 
so that 
(cf. Fig.).
Figure: a012660a
If 
and 
are anti-parallel with respect to 
and 
, then 
and 
are also anti-parallel with respect to 
and 
. In any quadrilateral inscribed in a circle, any two opposite sides are anti-parallel with respect to the other two sides. If the lines 
and 
intersect at a point 
, one also says that 
and 
are anti-parallel with respect to the angle 
. If the lines 
and 
coincide, 
and 
are said to be anti-parallel with respect to a straight line.
How to Cite This Entry:
Anti-parallel straight lines. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Anti-parallel_straight_lines&oldid=31542
Anti-parallel straight lines. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Anti-parallel_straight_lines&oldid=31542
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article