Divide moduli, subtract arguments: r1eiθ1r2eiθ2=r1r2ei(θ1−θ2)\frac{r_1 e^{i\theta_1}}{r_2 e^{i\theta_2}} = \frac{r_1}{r_2} e^{i(\theta_1-\theta_2)}r2eiθ2r1eiθ1=r2r1ei(θ1−θ2).
