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

      From cppreference.com
      <cpp‎ |numeric‎ |math
       
       
       
      Common mathematical functions
      Nearest integer floating point operations
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      Floating point manipulation functions
      (C++11)(C++11)
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      Classification and comparison
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      Types
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      Macro constants
       
      Defined in header<cmath>
      (1)
      float       acos(float num);

      double      acos(double num);

      longdouble acos(longdouble 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)
      longdouble acosl(longdouble num);
      (3)(since C++11)
      (constexpr since C++26)
      SIMD overload(since C++26)
      Defined in header<simd>
      template</*math-floating-point*/ V>

      constexpr/*deduced-simd-t*/<V>

                  acos(const V& v_num);
      (S)(since C++26)
      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 ofnum. The library provides overloads ofstd::acos for all cv-unqualified floating-point types as the type of the parameter.(since C++23)
      S) The SIMD overload performs an element-wisestd::acos onv_num.
      (Seemath-floating-point anddeduced-simd-t for their definitions.)
      (since C++26)
      A) Additional overloads are provided for all integer types, which are treated asdouble.
      (since C++11)

      Contents

      [edit]Parameters

      num - floating-point or integer value

      [edit]Return value

      If no errors occur, the arc cosine ofnum (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 inmath_errhandling.

      Domain error occurs ifnum is outside the range[-1.01.0].

      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 argumentnum of integer type,std::acos(num) has the same effect asstd::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 handlingerrno=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) = 3.14159acos(0.0) = 1.57082*acos(0.0) = 3.14159acos(0.5) = 1.04723*acos(0.5) = 3.14159acos(1) = 0acos(1.1) = nan    errno == EDOM: Numerical argument out of domain    FE_INVALID raised

      [edit]See also

      (C++11)(C++11)
      computes arc sine (\({\small\arcsin{x}}\)arcsin(x))
      (function)[edit]
      (C++11)(C++11)
      computes arc tangent (\({\small\arctan{x}}\)arctan(x))
      (function)[edit]
      (C++11)(C++11)
      arc tangent, using signs to determine quadrants
      (function)[edit]
      (C++11)(C++11)
      computes cosine (\({\small\cos{x}}\)cos(x))
      (function)[edit]
      computes arc cosine of a complex number (\({\small\arccos{z}}\)arccos(z))
      (function template)[edit]
      applies the functionstd::acos to each element of valarray
      (function template)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/math/acos&oldid=154198"

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