atan(), atanf()

arc tangent function of one variable 

Function

SYNOPSIS

#include <math.h>

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 [-Pi/2, +Pi/2].

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

The atanf() function is a single-precision version of atan().

PARAMETERS

x 

Is the value from which to derive the principle value of the arc tangent.

RETURN VALUES

The atan() function returns the arc tangent in the range [-pi/2, +pi/2] radians.

If the value of x is NaN, NaN is returned and if in POSIX mode, errno is set to EDOM.

If the result underflows, 0.0 is returned and if in POSIX mode, errno is set to ERANGE. If in SVID or XOPEN mode, the matherr() function is also called.

CONFORMANCE

atan(): ANSI/ISO 9899-1990

atanf(): MKS Toolkit UNIX APIs extension

MULTITHREAD SAFETY LEVEL

MT-Safe.

PORTING ISSUES

At high levels of compiler optimizations, the hardware handles the atan() function intrinsically. In such cases, mathematical exceptions do not cause the matherr() function to be called or the errno value to be set.

AVAILABILITY

MKS Toolkit for Professional Developers
MKS Toolkit for Enterprise Developers
MKS Toolkit for Enterprise Developers 64-Bit Edition

SEE ALSO

Functions:
acos(), asin(), atan2(), cos(), cosh(), math(), matherr(), sin(), sinh(), tan(), tanh()

MKS Toolkit 9.2 Documentation Build 16.