6.5. Roots of unity and other numbers. The polar expression of multiplication is useful in nding roots of complex numbers. Begin with the sixth roots of 1, for example. We are looking for complex numbers zsuch that z6 = 1. Since moduli multiply, jzj6 = jz6j= j1j= 1, and since moduli are nonnegative this forces jzj= 1: all the sixth roots of