4. Show that any complex number of norm 1 (except -1) can be written in the form z = (1 + it)/(1 − it) for some t E R.

We have to prove that any complex number of norm $1$ (except $-1$) can be written in the form

 $z=\frac{1+it}{1-it}$ for some $t\in \mathrm{ℝ}$