# What determines when a line change is made?

Sometimes the coach makes the decision as to when and who changes lines. Most of the time the players will change on the fly(which means they change while play is going on). That is when the coach decides the line that goes on but not when. The coach chooses when only during a stoppage in play.

### Some lines have no slope?

A horizontal line has a slope of zero. For a vertical line, the slope is not defined (change of y / change of x would result in a division by zero). A horizontal line has a slope of zero. For a vertical line, the slope is not defined (change of y / change of x would result in a division by zero). A horizontal line has a slope of zero. For a vertical line, the…