In this video the tutor shows when to use a dotted line and when to use a solid line while graphing lines in coordinate geometry. He says that we should use a dotted line to plot an inequality which contains the symbols less than or greater than. He also says that we should use a straight line when plotting an inequality which contains the signs less than or equal to and greater than or equal to. He goes on and demonstrates this idea with some examples. This video shows how to use different lines while plotting inequalities on a graph.