std:: acos, std:: acosf, std:: acosl

Parameters

Return value

If no errors occur, the arc cosine of num ( arccos(num) ) in the range [0, π] , is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling .

Domain error occurs if num is outside the range [ - 1.0 , 1.0 ] .

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is +1 , the value +0 is returned.
• If |num| > 1 , a domain error occurs and NaN is returned.
• if the argument is NaN, NaN is returned.

Notes

The additional overloads are not required to be provided exactly as (A) . They only need to be sufficient to ensure that for their argument num of integer type, std :: acos ( num ) has the same effect as std :: acos ( static_cast < double > ( num ) ) .

Example

#include <cerrno>
#include <cfenv>
#include <cmath>
#include <cstring>
#include <iostream>
 
// #pragma STDC FENV_ACCESS ON
 
int main()
{
    std::cout << "acos(-1) = " << std::acos(-1) << '\n'
              << "acos(0.0) = " << std::acos(0.0) << '\n'
              << "2*acos(0.0) = " << 2 * std::acos(0) << '\n'
              << "acos(0.5) = " << std::acos(0.5) << '\n'
              << "3*acos(0.5) = " << 3 * std::acos(0.5) << '\n'
              << "acos(1) = " << std::acos(1) << '\n';
 
    // error handling
    errno = 0;
    std::feclearexcept(FE_ALL_EXCEPT);
 
    std::cout << "acos(1.1) = " << std::acos(1.1) << '\n';
 
    if (errno == EDOM)
        std::cout << "    errno == EDOM: " << std::strerror(errno) << '\n';
    if (std::fetestexcept(FE_INVALID))
        std::cout << "    FE_INVALID raised" << '\n';
}

acos(-1) = 3.14159
acos(0.0) = 1.5708
2*acos(0.0) = 3.14159
acos(0.5) = 1.0472
3*acos(0.5) = 3.14159
acos(1) = 0
acos(1.1) = nan
    errno == EDOM: Numerical argument out of domain
    FE_INVALID raised

See also