[Bug-gsl] [bug #55412] Bessel function returns incorrect value

[Vladimir Khodygo]

URL:
  <https://savannah.gnu.org/bugs/?55412>

                 Summary: Bessel function returns incorrect value
                 Project: GNU Scientific Library
            Submitted by: vladk
            Submitted on: Mon 07 Jan 2019 05:59:39 PM UTC
                Category: Documentation
                Severity: 3 - Normal
        Operating System: 
                  Status: None
             Assigned to: None
             Open/Closed: Open
                 Release: any
         Discussion Lock: Any

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Details:

If you run 

# include <stdio.h> 
# include <gsl/gsl_sf_bessel.h> 
int main (void)
{
double x = 5.0; 
double y = gsl_sf_bessel_j0 (x); 
printf ("J0(%g) = %.18e\n", x, y);
return(0);
}


you get 

JO(5) =  -1.917848549326277019e-01


That is correct answer according to the definition sin(x)/x.
However, the documentation says that the answer is 
J0(5) = -1.775967713143382642e-01





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