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

DERIVATION

Derived from Issue 1 of the SVID.