acosf(3) Linux Man Page - System Grab Bag

Name

acos, acosf, acosl - arc cosine function

Library

Math library ( libm ", " -lm )

Synopsis

#include <math.h> 
double acos(double  x );
float acosf(float  x );
long double acosl(long double  x );

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

acosf() acosl()

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

Description

These functions calculate the arc cosine of x ; that is the value whose cosine is x.

Return Value

On success, these functions return the arc cosine of x in radians; the return value is in the range [0,\ pi].

If x is a NaN, a NaN is returned.

If x is +1, +0 is returned.

If x is positive infinity or negative infinity, a domain error occurs, and a NaN is returned.

If x is outside the range [-1,\ 1], a domain error occurs, and a NaN is returned.

Errors

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x is outside the range [-1,\ 1] errno is set to EDOM .An invalid floating-point exception ( FE_INVALID ) is raised.

Attributes

For an explanation of the terms used in this section, see attributes(7). allbox; lbx lb lb T{ acos()acosf()acosl()

Interface	Attribute	Value
T}	Thread safety	MT-Safe

Standards

C11, POSIX.1-2008.

History

C99, POSIX.1-2001.

The variant returning double also conforms to C89, SVr4, 4.3BSD.