If two lines in the same plane intersect to form a right angle, then their slopes are negative reciprocals. Representing their slopes by sa and sb, then sa = -1/sb .
perpendicular lines.
They can be, but not necessarily. If two lines in the same plane never intersect, they are parallel. Though, two lines can exist in the same plane without being parallel. Ie, two lines that intersect at a 90 degree angle are perpendicular. Most lines in a plane aren't parallel.
Angle. Also, two lines which intersect at a point can define a plane.
Parallel lines in the Euclidean plane do not intersect but all parallel lines in the projective plane intersect at the point at infinity.
Lines which are parallel. All other lines on the same plane eventually intersect.
perpendicular lines.
Lines in the same plane that do not intersect Lines in the same plane that do not intersect Lines in the same plane that do not intersect Lines in the same plane that do not intersect
a coordinate plane
Their are Perpendicular.
They can be, but not necessarily. If two lines in the same plane never intersect, they are parallel. Though, two lines can exist in the same plane without being parallel. Ie, two lines that intersect at a 90 degree angle are perpendicular. Most lines in a plane aren't parallel.
All non-parallel lines in a plane will intersect at some point in the plane.
They have the same angle relative to any plane or line and never intersect.
Two lines that do not intersect on the same plane are Parallel lines.
Angle. Also, two lines which intersect at a point can define a plane.
Parallel lines in the Euclidean plane do not intersect but all parallel lines in the projective plane intersect at the point at infinity.
Lines which are parallel. All other lines on the same plane eventually intersect.
If the two lines lie in the same plane, and they do not intersect, then they are parallel. If they are not in the same plane, and do not intersect, then they are called skew lines.