what are perpendicular lines definition
Perpendicular Lines. Quatr.us Math Geometry Lines. Perpendicular lines. Two lines are perpendicular if they cross at right angles. You can test this by extending the lines until they cross (if they do not cross then they are parallel).erpendicular Lines. Quatr.us Math Geometry Lines. Perpendicular lines. Two lines are perpendicular if they cross at right angles. You can test this by extending the lines until they cross (if they do not cross then they are parallel).