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
\[\operatorname{Cl_2}(\theta) =
\operatorname{Im} \operatorname{Li_2}(\exp(i\theta)).\]
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gsl_sf_clausen(x)¶
This routine computes the Clausen integral \(\operatorname{Cl_2}(x)\).