atan, atanf, atanl, atand32, atand64, and atand128 Subroutines

Purpose

Computes the arc tangent.

Syntax

#include <math.h>

float atanf (x)
float x;

long double atanl (x)
long double x;

double atan (x)
double x;
_Decimal32 atand32 (x)
_Decimal32 x;

_Decimal64 atand64 (x)
_Decimal64 x;

_Decimal128 atand128 (x)
_Decimal128 x;

Description

The atanf, atanl, atan, atand32, atand64, and atand128 subroutines compute the principal value of the arc tangent of the x parameter.

An application wishing to check for error situations should set the errno global variable to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has occurred.

Parameters

Return Values

Upon successful completion, the atanf, atanl, atan, atand32, atand64, and atand128 subroutines return the arc tangent of x in the range [-pi /2, pi/2] radians.

If x is NaN, a NaN is returned.

If x is 0, x is returned.

If x is ±Inf, ±x/2 is returned.

If x is subnormal, a range error may occur and x is returned.