Sketch a phasor diagram to illustrate the resultant of E1 = E01 sin wt and E2 = E02 sin (wt + ǿ), where E02 = 1.50E01 and π/6 < ǿ < π/3. Use the sketch and the law of cosines to show that, for two coherent waves, the resultant intensity can be written in the form IR = I1 + I2 + 2 I1I2 cos ǿ.