I think it, once the values for p,r and q are found you can sub them into the equation,so it is now 4cos2x-3=0. cos2x= 3/4, so you get cos-1(3/4)=2x. therefore 2x= + or - 0.723,5.560 and 7.006. Hence x would equal half of each of these values? It seems a lot easier now I have all the values!