1 @cindex Clausen functions
3 The Clausen function is defined by the following integral,
7 Cl_2(x) = - \int_0^x dt \log(2 \sin(t/2))
14 Cl_2(x) = - \int_0^x dt \log(2 \sin(t/2))
19 It is related to the dilogarithm by
20 @c{$Cl_2(\theta) = \Im(Li_2(e^{i\theta}))$}
21 @math{Cl_2(\theta) = \Im Li_2(\exp(i\theta))}.
22 The Clausen functions are declared in the header file
23 @file{gsl_sf_clausen.h}.
25 @deftypefun double gsl_sf_clausen (double @var{x})
26 @deftypefunx int gsl_sf_clausen_e (double @var{x}, gsl_sf_result * @var{result})
27 These routines compute the Clausen integral @math{Cl_2(x)}.