`acos.3p` ( 3 )

функции арккосинуса (arc cosine functions)

Пролог (Prolog)

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Имя (Name)

acos, acosf, acosl — arc cosine functions

Синопсис (Synopsis)

#include <math.h>

double acos(double x); float acosf(float x); long double acosl(long double x);

Описание (Description)

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard.

These functions shall compute the principal value of the arc cosine of their argument x. The value of x should be in the range [-1,1].

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

Возвращаемое значение (Return value)

Upon successful completion, these functions shall return the arc cosine of x, in the range [0,π] radians.

For finite values of x not in the range [-1,1], a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.

If x is NaN, a NaN shall be returned.

If x is +1, +0 shall be returned.

If x is ±Inf, a domain error shall occur, and a NaN shall be returned.

Ошибки (Error)

These functions shall fail if:

Domain Error The x argument is finite and is not in the range [-1,1], or is ±Inf.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

The following sections are informative.

Примеры (Examples)

None.

Использование в приложениях (Application usage)

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

Обоснование (Rationale)

None.

Будущие направления (Future directions)