How is Im$[(z_1+z_2)(z_2+z_3)(z_3+z_1)]/(z_1 z_2 z_3) = 0$

51 Views Asked by At

How is Im$\frac{[(z_1+z_2)(z_2+z_3)(z_3+z_1)]}{(z_1 z_2 z_3)} = 0$ if $|z_1|=|z_2|=|z_3|=1$? My book says it is because $\frac{[(z_1+z_2)(z_2+z_3)(z_3+z_1)]}{(z_1 z_2 z_3)}$ is equal to its conjugate, but I don't see how it is possible. Would someone please help?