I doubt your teacher said that there was no graph. He/she may well have said that this is not a "function". That is, that there can be two different y values for one x value. As for graphing it, the simplest thing to do is to calculate values and mark those points. For example, if x= 0, then so that . Mark the two points (0, R) and (0, -R). If x= R/4, then so so also. another two points on the graph are (R/4, R/4) and (R/4, -R/4). If x= R, the equation becomes which leads to and y= 0. The point (R, 0) is on the graph.