NAME

atan — arc tangent function

SYNOPSIS

#include <math.h>

double atan(double x);

DESCRIPTION

The atan() function computes the principal value of the arc tangent of x .

An application wishing to check for error situations should set errno to 0 before calling atan(). If errno is non-zero on return, or the return value is NaN, an error has occurred.

RETURN VALUE

Upon successful completion, atan() returns the arc tangent of x in the range [-/2, /2] radians.

If x is NaN, NaN is returned and errno may be set to [EDOM].

If the result underflows, 0.0 is returned and errno may be set to [ERANGE].

ERRORS

The atan() function may fail if:

[EDOM]

The value of x is NaN.

[ERANGE]

The result underflows.

No other errors will occur.

EXAMPLES

None.

APPLICATION USAGE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

atan2(3) , isnan(3) , tan(3) , <math.h> .

DERIVATION

Derived from Issue 1 of the SVID.