< cpp‎ | numeric‎ | valarray
Defined in header <valarray>
template< class T >
valarray<T> acos( const valarray<T>& va );

For each element in va computes arc cosine of the value of the element.


[edit] Parameters

va - value array to apply the operation to

[edit] Return value

Value array containing arc cosines of the values in va.

[edit] Notes

Unqualified function (acos) is used to perform the computation. If such function is not available, std::acos is used due to argument dependent lookup.

The function can be implemented with the return type different from std::valarray. In this case, the replacement type has the following properties:

[edit] Possible implementation

template<class T>
valarray<T> acos(const valarray<T>& va)
    valarray<T> other = va;
    for (T &i : other) {
        i = acos(i);
    return other;

[edit] Example

#include <cmath>
#include <iostream>
#include <valarray>
const double pi = 4.0 * atan(1.0);
int main()
    // take common x-values from unit circle
    std::valarray<double> v1 = {-1.0, -sqrt(3.0)/2.0, -sqrt(2.0)/2.0, -0.5, 0.0, 0.5, sqrt(2.0)/2.0, sqrt(3.0)/2.0, 1.0};
    std::valarray<double> v2 = std::acos(v1) * 180.0 / pi;;
    for(double n : v2)
        std::cout << std::fixed << n << ' ';
    std::cout << '\n';


180.000000 150.000000 135.000000 120.000000 90.000000 60.000000 45.000000 30.000000 0.000000

[edit] See also

applies the function std::asin to each element of valarray
(function template) [edit]
applies the function std::atan to each element of valarray
(function template) [edit]
applies the function std::atan2 to a valarray and a value
(function template) [edit]
applies the function std::cos to each element of valarray
(function template) [edit]
computes arc cosine (arccos(x))
(function) [edit]
computes arc cosine of a complex number (arccos(z))
(function template) [edit]