A complex variable function analytic in can be written as...

(1)

If in (1) is then is also analytic in and is...

(2)

A direct way to compute the from the is given by the identity we obtain combining (1) and (2)...

(3)

... so that is...

(4)

If we perform the substitution of variable so that is...

(5)

The conclusion is that if...

(6)

... then it is also...

(7)

Kind regards