tgamma

Returns the value of Gamma function for the argument x0.

The Gamma function is defined by Gamma(x) = integral from 0 to infinity of t^(x-1) e^-t dt.

It is defined for every real number except for non-positive integers. For non-negative integral m one has Gamma(m+1) = m! and, more generally, for all x: Gamma(x+1) = x * Gamma(x).

Furthermore, the following is valid for all values of x outside the poles: Gamma(x) * Gamma(1 - x) = PI / sin(PI * x)

This function return the value of Gamma function for the argument x. It had to be called "true gamma function" since there is already a function gamma that returns something else.

Parameters:

x0	A numeric value.