Posts: 380

Threads: 78

Joined: Dec 2010

Is it possible to define a function

h(h(z)) = |z|, h(z) =/= |z|

or

h(h(z)) = arg(z)

I wonder because these seem like difficult functions to crack, considering they have no Taylor series.

Posts: 27

Threads: 3

Joined: Apr 2009

(03/31/2011, 08:28 PM)JmsNxn Wrote: Is it possible to define a function

h(h(z)) = |z|, h(z) =/= |z|

or

h(h(z)) = arg(z)

I wonder because these seem like difficult functions to crack, considering they have no Taylor series.

We could set h(z) = |z| for z with non-negative real part, h(z) = -iz for z with negative real and non-negative imaginary part, and h(z) = iz for z with negative and imaginary parts. Then we'd get h(h(z)) = |z| for all z. A similar technique should work for h(h(z)) = arg(z).

Posts: 380

Threads: 78

Joined: Dec 2010

that was easy