PSI _ _ _ _ _ _ _ _ _ _ _ _ operator

The Psi operator returns the Psi (or DiGamma) function.

Psi(x) := df(Gamma(z),z)/ Gamma (z)

syntax:

examples:

Psi(3); 

  (2*log(2) + psi(1/2) + psi(1) + 3)/2 


on rounded; 

- Psi(1); 

  0.577215664902

Euler's constant can be found as - Psi(1).