May 2, 1991 ATAN 3

### NAME

atan, atanf - arc tangent function of one variable

### LIBRARY

Math Library (libm, -lm)

### SYNOPSIS

```double` atan(```double x`)
```float` atanf(```float x`)

### DESCRIPTION

The atan(``) and atanf(``) functions compute the principal value of the arc tangent of ```x` in the range [-/2, +/2].

### SEE ALSO

acos(3), asin(3), atan2(3), cos(3), cosh(3), math(3), sin(3), sinh(3), tan(3), tanh(3)

### STANDARDS

The atan(``) functions conforms to ANSI X3.159-1989 (``ANSI C89'') .