The following functions allow for the propagation of errors when
combining quantities by multiplication. The functions are declared in
the header file gsl_sf_elementary.h.
— Function: int gsl_sf_multiply_e (double x, double y, gsl_sf_result * result)
This function multiplies x and y storing the product and its
associated error in result.
— Function: int gsl_sf_multiply_err_e (double x, double dx, double y, double dy, gsl_sf_result * result)
This function multiplies x and y with associated absolute
errors dx and dy. The product
xy +/- xy \sqrt((dx/x)^2 +(dy/y)^2)
is stored in result.