TriGamma

TriGamma(x)

TriGamma function.

\Psi_1(x) = \frac{1}{\Gamma(x)}\frac{\mathrm{d}^2 \Gamma(x)}{\mathrm{d}x^2}

with \Gamma the Gamma function.

Parameters:
xfloat \in \Rset^*_+
Returns:
resultfloat