The angles of links 3 and 4 can be measured with a protractor. One circruit has angles O3 and O4 the other O3 and O4 A graphical solution is only valid for the particular value of input angle used. For each additional position analysis we must completely redraw the linkage linkage. This can become burdensome if we need a complete analysis at every 1 or 2 degree increment of O2 In that case we will be better off to derive an analytical solution for O3 and which can be solved by computer.