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dawsn

Dawson's Integral.

SYNOPSIS:

double x, y, dawsn();
y = dawsn(x);

DESCRIPTION:

Approximates the integral

                             x
                             -
                      2     | |        2
  dawsn(x)  =  exp( -x  )   |    exp( t  ) dt
                          | |
                           -
                           0

Three different rational approximations are employed, for the intervals 0 to 3.25; 3.25 to 6.25; and 6.25 up.

ACCURACY:

                      Relative error:
arithmetic   domain     # trials      peak         rms
    IEEE      0,10        10000       6.9e-16     1.0e-16
    DEC       0,10         6000       7.4e-17     1.4e-17