# Clausen Function¶

The Clausen function is defined by the following integral,

$\operatorname{Cl_2}(x) = -\int_0^x \log(2 \sin(t/2)) dt$

It is related to the dilogarithm by

$\operatorname{Cl_2}(\theta) = \operatorname{Im} \operatorname{Li_2}(\exp(i\theta)).$
gsl_sf_clausen(x)

This routine computes the Clausen integral $$\operatorname{Cl_2}(x)$$.