std::acos, std::acosf, std::acosl
<cmath>
double acos ( double num );
acos ( /*floating-point-type*/ num );
(constexpr since C++26)
(constexpr since C++26)
(constexpr since C++26)
<simd>
constexpr /*deduced-simd-t*/<V>
<cmath>
double acos ( Integer num );
std::acos for all cv-unqualified floating-point types as the type of the parameter.(since C++23)std::acos on v_num.- (See math-floating-point and deduced-simd-t for their definitions.)
[edit] Parameters
[edit] 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.
[edit] 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
+0is returned. - If |num| > 1, a domain error occurs and NaN is returned.
- if the argument is NaN, NaN is returned.
[edit] 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)).
[edit] 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'; }
Output:
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
[edit] See also
(function template) [edit]