Complex Arithmetic/Examples/Modulus of ((z 1 + z 2 + 1) (z 1 - z 2 + i)^-1)

Example of Complex Arithmetic
Let $z_1 = 1 - i$ and $z_2 = -2 + 4 i$.

Then:
 * $\cmod {\dfrac {z_1 + z_2 + 1} {z_1 - z_2 + i} } = \dfrac 3 5$