Oscilloscopes generally plots time X-axis. They also provide and X-Y mode, where one input is plotted on the X-axis. This feature is used for showing lissajou's figures and also for measuring the phase difference of two input waveforms.
Plot two signals in the X-Y mode and find out their phase difference. The phase difference is be generated by CR circuit.
The phase difference is given by the equation θ = sin − 1((yint)/(ymax))
There is an option to plot (A1-A2) against A2. In the above circuit, this plots the voltage across the capacitor against the voltage across the resistor.