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

From cppreference.com
< cpp‎ | numeric‎ | math
m (Text replace - "Integral arg" to "IntegralType arg")
(Use declarations template)
 
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{{cpp/title|acos}}
+
{{cpp/title|acos|acosf|acosl}}
 
{{cpp/numeric/math/navbar}}
 
{{cpp/numeric/math/navbar}}
−
{{dcl begin}}
+
{{cpp/numeric/math/declarations
−
{{dcl header | cmath}}
+
|family=acos
−
{{dcl |num=1|
+
|param1=num
−
float      acos( float arg );
+
|constexpr_since=26
 +
|desc=Computes the principal value of the arc cosine of {{c|num}}.
 
}}
 
}}
−
{{dcl |num=2|
 
−
double      acos( double arg );
 
−
}}
 
−
{{dcl |num=3|
 
−
long double acos( long double arg );
 
−
}}
 
−
{{dcl |num=4|since=c++11 |
 
−
double      acos( IntegralType arg );
 
−
}}
 
−
{{dcl end}}
 
−
 
−
Computes the principal value of the arc cosine of {{tt|arg}}.
 
−
@4@ A set of overloads or a function template accepting an argument of any [[cpp/types/is_integral|integral type]]. Equivalent to 2) (the argument is cast to {{c|double}}).
 
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
−
{{par | arg | value of a floating-point or [[cpp/types/is_integral|Integral type]]}}
+
{{par|num|floating-point or integer value}}
 
{{par end}}
 
{{par end}}
  
 
===Return value===
 
===Return value===
−
If no errors occur, the arc cosine of {{tt|arg}} ({{math|arccos(arg)}}) in the range {{math|[0 , &pi;]}}, is returned.
+
If no errors occur, the arc cosine of {{c|num}} ({{math|arccos(num)}}) in the range {{math|[0, &pi;]}}, is returned.
  
−
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
+
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.
 
If a range error occurs due to underflow, the correct result (after rounding) is returned.
  
 
===Error handling===
 
===Error handling===
−
Errors are reported as specified in [[cpp/numeric/math/math_errhandling|math_errhandling]]
+
Errors are reported as specified in {{lc|math_errhandling}}.
  
−
Domain error occurs if {{tt|arg}} is outside the range {{tt|[-1.0, 1.0]}}
+
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 implementation supports IEEE floating-point arithmetic (IEC 60559),
 
* If the argument is {{math|+1}}, the value {{tt|+0}} is returned.
 
* If the argument is {{math|+1}}, the value {{tt|+0}} is returned.
−
* If {{math|{{!}}arg{{!}} > 1}}, a domain error occurs and NaN is returned.
+
* If {{math|{{!}}num{{!}} > 1}}, a domain error occurs and NaN is returned.
−
* if the argument is NaN, 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 <cmath>
+
−
#include <iostream>
+
 
#include <cerrno>
 
#include <cerrno>
 
#include <cfenv>
 
#include <cfenv>
 +
#include <cmath>
 
#include <cstring>
 
#include <cstring>
 +
#include <iostream>
 +
 +
// #pragma STDC FENV_ACCESS ON
  
−
#pragma STDC FENV_ACCESS ON
 
 
int main()
 
int main()
 
{
 
{
−
     std::cout << "acos(-1) = " << acos(-1) << '\n'
+
     std::cout << "acos(-1) = " << std::acos(-1) << '\n'
−
               << "acos(0.0) = " << acos(0.0) << " 2*acos(0.0) = " << 2*acos(0) << '\n'
+
               << "acos(0.0) = " << std::acos(0.0) << '\n'
−
               << "acos(0.5) = " << acos(0.5) << " 3*acos(0.5) = " << 3*acos(0.5) << '\n'
+
              << "2*acos(0.0) = " << 2 * std::acos(0) << '\n'
−
               << "acos(1) = " << acos(1) << '\n';
+
               << "acos(0.5) = " << std::acos(0.5) << '\n'
−
     // error handling  
+
              << "3*acos(0.5) = " << 3 * std::acos(0.5) << '\n'
−
     errno = 0; std::feclearexcept(FE_ALL_EXCEPT);
+
               << "acos(1) = " << std::acos(1) << '\n';
−
     std::cout << "acos(1.1) = " << acos(1.1) << '\n';
+
   
−
     if(errno == EDOM)
+
     // 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';
 
         std::cout << "    errno == EDOM: " << std::strerror(errno) << '\n';
−
     if(std::fetestexcept(FE_INVALID))
+
     if (std::fetestexcept(FE_INVALID))
 
         std::cout << "    FE_INVALID raised" << '\n';
 
         std::cout << "    FE_INVALID raised" << '\n';
 
}
 
}
−
| output=
+
|output=
 
acos(-1) = 3.14159
 
acos(-1) = 3.14159
−
acos(0.0) = 1.5708 2*acos(0.0) = 3.14159
+
acos(0.0) = 1.5708
−
acos(0.5) = 1.0472 3*acos(0.5) = 3.14159
+
2*acos(0.0) = 3.14159
 +
acos(0.5) = 1.0472
 +
3*acos(0.5) = 3.14159
 
acos(1) = 0
 
acos(1) = 0
 
acos(1.1) = nan
 
acos(1.1) = nan
Line 78: Line 78:
 
===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/numeric/math/dsc asin}}
+
{{dsc inc|cpp/numeric/math/dsc asin}}
−
{{dsc inc | cpp/numeric/math/dsc atan}}
+
{{dsc inc|cpp/numeric/math/dsc atan}}
−
{{dsc inc | cpp/numeric/math/dsc atan2}}
+
{{dsc inc|cpp/numeric/math/dsc atan2}}
−
{{dsc inc | cpp/numeric/math/dsc cos}}
+
{{dsc inc|cpp/numeric/math/dsc cos}}
−
{{dsc inc | cpp/numeric/complex/dsc acos}}
+
{{dsc inc|cpp/numeric/complex/dsc acos}}
−
{{dsc inc | cpp/numeric/valarray/dsc acos}}
+
{{dsc inc|cpp/numeric/valarray/dsc acos}}
−
{{dsc see c | c/numeric/math/acos}}
+
{{dsc see c|c/numeric/math/acos}}
 
{{dsc end}}
 
{{dsc end}}
  
 
{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}}
 
{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}}

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
Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/acos&oldid=154198"