April 20, 1991 ERF 3

### NAME

erf, erff, erfc, erfcf - error function operators

### LIBRARY

Math Library (libm, -lm)

### SYNOPSIS

```double` erf(```double x`)
```float` erff(```float x`)
```double` erfc(```double x`)
```float` erfcf(```float x`)

### DESCRIPTION

These functions calculate the error function of ```x`.

The erf(``) calculates the error function of x; where

      erf(x) = 2/sqrt(pi)*integral from 0 to x of exp(-t*t) dt.

The erfc(``) function calculates the complementary error function of ```x`; that is erfc(``) subtracts the result of the error function erf(```x`) from 1.0. This is useful, since for large ```x` places disappear.

### SEE ALSO

math(3)

### HISTORY

The erf(``) and erfc(``) functions appeared in 4.3BSD.