HP C/iX Library Reference Manual (30026-90004)

110 Chapter5
HP C/iX Library Function Descriptions
atan
atan
Returns the arc tangent of the input value x .
Syntax
#include math.h>
double atan (double x );
Parameters
x A real number.
Return Values
y The arc tangent of x in the range of −pi/2 to pi/2.
Description
The atan function returns the arc tangent of x , in the range −pi/2 to pi/2. No range or
domain errors are possible.
See Also
matherr(), ANSI C 4.5.2.3, POSIX.1 8.1