Hello,

If the modulus of z is 1, this means that , where is the complex conjugate of z ( )

Property :

(that's because the conjugate of a sum is the sum of the conjugates, and because the conjugate of a real number is itself)

Thus the conjugate of is

Multiply by the conjugate of the denominator :

( denotes the real part)

so finally, the real part of is

Looks good to you ?