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     ERF(S)                    UNIX System V                    ERF(S)



     Name
          erf, erfc - error function and complementary error function

     Syntax
          #include <math.h>

          double erf (x)
          double x;

          double erfc (x)
          double x;

     Descripxion
          The erf function returns the error function of x, defined as
          plus or minus 2 over the square root of pi multiplied by the
          integral from 0 to x of e to negative t squared power.

          erfc, which returns 1.0 - erf(x), is provided because of the
          extreme loss of relative accuracy if erf(x) is called for
          large x and the result subtracted from 1.0 (e.g., for x = 5,
          12 places are lost).

     See Also
          exp(S)

     Standards Conformance
          erf and erfc are conformant with:
          AT&T SVID Issue 2, Select Code 307-127;
          and The X/Open Portability Guide II of January 1987.

                                                (printed 6/20/89)