<P> These formulas still give the correct point coordinates even if the parallel lines are horizontal (i.e., m = 0). The distance between the points is </P> <Dl> <Dd> d = (b 1 m − b 2 m m 2 + 1) 2 + (b 2 − b 1 m 2 + 1) 2, (\ displaystyle d = (\ sqrt (\ left ((\ frac (b_ (1) m - b_ (2) m) (m ^ (2) + 1)) \ right) ^ (2) + \ left ((\ frac (b_ (2) - b_ (1)) (m ^ (2) + 1)) \ right) ^ (2))) \,,) </Dd> </Dl> <Dd> d = (b 1 m − b 2 m m 2 + 1) 2 + (b 2 − b 1 m 2 + 1) 2, (\ displaystyle d = (\ sqrt (\ left ((\ frac (b_ (1) m - b_ (2) m) (m ^ (2) + 1)) \ right) ^ (2) + \ left ((\ frac (b_ (2) - b_ (1)) (m ^ (2) + 1)) \ right) ^ (2))) \,,) </Dd> <P> which reduces to </P>

A pair of lines that cross or will eventually cross