Random: double gsl_ran_rayleigh_tail(const gsl_rng * r, double a double sigma)
This function returns a random variate from the tail of the Rayleigh
distribution with scale parameter sigma and a lower limit of
a. The distribution is,
Function: double gsl_ran_rayleigh_tail_pdf(double x, double a, double sigma)
This function computes the probability density p(x) at x
for a Rayleigh tail distribution with scale parameter sigma and
lower limit a, using the formula given above.