Parallel lines are indicated by arrows going in the same direction. Parallel lines are indicated by arrows going in the same direction. If there is more than one set of parallel lines in a diagram, ...

Parallel lines are straight lines which have the same direction and so never meet. Arrowheads show lines are parallel. A straight line that cuts a pair of parallel lines is called an intersecting ...

Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.