| Defined in header <cmath> | ||
|---|---|---|
float acos( float arg ); | (1) | |
double acos( double arg ); | (2) | |
long double acos( long double arg ); | (3) | |
double acos( Integral arg ); | (4) | (since C++11) |
Computes the principal value of the arc cosine of arg.
4) A set of overloads or a function template accepting an argument of any integral type. Equivalent to 2) (the argument is cast to
double).Parameters
| arg | - | value of a floating-point or Integral type |
Return value
If no errors occur, the arc cosine of arg (arccos(arg)) 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 arg 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 |arg| > 1, a domain error occurs and NaN is returned.
- if the argument is NaN, NaN is returned
Example
#include <cmath>
#include <iostream>
#include <cerrno>
#include <cfenv>
#include <cstring>
#pragma STDC FENV_ACCESS ON
int main()
{
std::cout << "acos(-1) = " << acos(-1) << '\n'
<< "acos(0.0) = " << acos(0.0) << " 2*acos(0.0) = " << 2*acos(0) << '\n'
<< "acos(0.5) = " << acos(0.5) << " 3*acos(0.5) = " << 3*acos(0.5) << '\n'
<< "acos(1) = " << acos(1) << '\n';
// error handling
errno = 0; std::feclearexcept(FE_ALL_EXCEPT);
std::cout << "acos(1.1) = " << 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 raisedSee also
| computes arc sine (arcsin(x)) (function) | |
| computes arc tangent (arctan(x)) (function) | |
| arc tangent, using signs to determine quadrants (function) | |
| computes cosine (cos(x)) (function) | |
| (C++11) | computes arc cosine of a complex number (arccos(z)) (function template) |
applies the function std::acos to each element of valarray (function template) | |
C documentation for acos | |
Please login to continue.