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Difference between revisions of "cpp/numeric/math/acos"

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< cpp‎ | numeric‎ | math
m (Use since= and until= params of {{dcl}} template.)
(Use declarations template)
 
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{{cpp/title|acos}}
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{{cpp/title|acos|acosf|acosl}}
 
{{cpp/numeric/math/navbar}}
 
{{cpp/numeric/math/navbar}}
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{{dcl begin}}
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{{cpp/numeric/math/declarations
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{{dcl header | cmath}}
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|family=acos
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{{dcl |
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|param1=num
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float      acos( float arg );
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|constexpr_since=26
 +
|desc=Computes the principal value of the arc cosine of {{c|num}}.
 
}}
 
}}
−
{{dcl |
 
−
double      acos( double arg );
 
−
}}
 
−
{{dcl |
 
−
long double acos( long double arg );
 
−
}}
 
−
{{dcl | since=c++11 |
 
−
double      acos( Integral arg );
 
−
}}
 
−
{{dcl end}}
 
−
 
−
Computes arc cosine of {{tt|arg}}
 
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
−
{{par | arg | floating point value}}
+
{{par|num|floating-point or integer value}}
 
{{par end}}
 
{{par end}}
  
 
===Return value===
 
===Return value===
−
Arc cosine of {{tt|arg}} in radians in the range of {{tt|[0; &pi;]}} radians.
+
If no errors occur, the arc cosine of {{c|num}} ({{math|arccos(num)}}) in the range {{math|[0, &pi;]}}, is returned.
  
−
Domain error occurs if {{tt|arg}} is outside the range {{tt|[-1.0; 1.0]}}. {{lc|NAN}} is returned in that case.
+
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 {{lc|math_errhandling}}.
 +
 
 +
Domain error occurs if {{c|num}} is outside the range {{closed range|-1.0|1.0}}.
 +
 
 +
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
 +
* If the argument is {{math|+1}}, the value {{tt|+0}} is returned.
 +
* If {{math|{{!}}num{{!}} > 1}}, a domain error occurs and NaN is returned.
 +
* if the argument is NaN, NaN is returned.
 +
 
 +
===Notes===
 +
{{cpp/numeric/math/additional integer overload note|acos}}
  
 
===Example===
 
===Example===
 
{{example
 
{{example
−
| code=
+
|code=
 +
#include <cerrno>
 +
#include <cfenv>
 
#include <cmath>
 
#include <cmath>
 +
#include <cstring>
 
#include <iostream>
 
#include <iostream>
 +
 +
// #pragma STDC FENV_ACCESS ON
  
 
int main()
 
int main()
 
{
 
{
−
     std::cout << "The number pi is " << std::acos(-1) << '\n';
+
     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=
+
|output=
−
The number pi is 3.14159
+
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===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/numeric/math/dsc asin}}
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{{dsc inc|cpp/numeric/math/dsc asin}}
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{{dsc inc | cpp/numeric/math/dsc atan}}
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{{dsc inc|cpp/numeric/math/dsc atan}}
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{{dsc inc | cpp/numeric/math/dsc atan2}}
+
{{dsc inc|cpp/numeric/math/dsc atan2}}
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{{dsc inc | cpp/numeric/math/dsc cos}}
+
{{dsc inc|cpp/numeric/math/dsc cos}}
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{{dsc inc | cpp/numeric/complex/dsc acos}}
+
{{dsc inc|cpp/numeric/complex/dsc acos}}
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{{dsc inc | cpp/numeric/valarray/dsc acos}}
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{{dsc inc|cpp/numeric/valarray/dsc acos}}
 +
{{dsc see c|c/numeric/math/acos}}
 
{{dsc end}}
 
{{dsc end}}
  
−
[[de:cpp/numeric/math/acos]]
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{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}}
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[[es:cpp/numeric/math/acos]]
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[[fr:cpp/numeric/math/acos]]
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[[it:cpp/numeric/math/acos]]
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−
[[ja:cpp/numeric/math/acos]]
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[[pl:cpp/numeric/math/acos]]
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[[pt:cpp/numeric/math/acos]]
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[[ru:cpp/numeric/math/acos]]
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−
[[zh:cpp/numeric/math/acos]]
+

Latest revision as of 08:37, 28 June 2023

 
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Defined in header <cmath>
(1)
float       acos ( float num );

double      acos ( double num );

long double acos ( long double num );
 (until C++23)
/* floating-point-type */
            acos ( /* floating-point-type */ num );
 (since C++23)
(constexpr since C++26)
float       acosf( float num );
 (2) (since C++11)
(constexpr since C++26)
long double acosl( long double num );
 (3) (since C++11)
(constexpr since C++26)
Additional overloads (since C++11)
Defined in header <cmath>
template< class Integer >
double      acos ( Integer num );
 (A) (constexpr since C++26)
1-3) Computes the principal value of the arc cosine of num. The library provides overloads of std::acos for all cv-unqualified floating-point types as the type of the parameter.(since C++23)
A) Additional overloads are provided for all integer types, which are treated as double.
 (since C++11)

Contents

[edit] Parameters

num - floating-point or integer value

[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 +0 is 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

Run this code
#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

(C++11)(C++11)
 computes arc sine (arcsin(x))
(function) [edit]
(C++11)(C++11)
 computes arc tangent (arctan(x))
(function) [edit]
(C++11)(C++11)
 arc tangent, using signs to determine quadrants
(function) [edit]
(C++11)(C++11)
 computes cosine (cos(x))
(function) [edit]
(C++11)
 computes arc cosine of a complex number (arccos(z))
(function template) [edit]
applies the function std::acos to each element of valarray
(function template) [edit]
C documentation for acos
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