# std::tan(std::valarray)

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< cpp‎ | numeric‎ | valarray

Defined in header `<valarray>` |  |
template< class T > valarray<T> tan( const valarray<T>& va ); |  |

For each element in va computes tangent of the value of the element.

### Parameters

va | - | value array to apply the operation to

### Return value

Value array containing tangents of the values in va.

### Notes

Unqualified function (tan) is used to perform the computation. If such function is not available, std::tan 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:

  - All const member functions of std::valarray are provided.
  - std::valarray, std::slice_array, std::gslice_array, std::mask_array and std::indirect_array can be constructed from the replacement type.
  - For every function taking a const std::valarray <T>& except `begin()` and `end()` (since C++11), identical functions taking the replacement types shall be added;
  - For every function taking two const std::valarray <T>& arguments, identical functions taking every combination of const std::valarray <T>& and replacement types shall be added.
  - The return type does not add more than two levels of template nesting over the most deeply-nested argument type.

### Possible implementation

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

        return other; // proxy object may be returned
    }

### Example

Run this code

    #include <cmath>
    #include <iostream>
    #include <valarray>

    auto show = [](char const* title, const std::valarray<double>& va)
    {
        std::cout << title << " :";
        for (auto x : va)
            std::cout << "  " << std::fixed << x;
        std::cout << '\n';
    };

    int main()
    {
        const std::valarray<double> x = {.0, .1, .2, .3};
        const std::valarray<double> y = std::tan(x);
        const std::valarray<double> z = std::atan(y);

        show("x          ", x);
        show("y = tan(x) ", y);
        show("z = atan(y)", z);
    }

Output:

    x           :  0.000000  0.100000  0.200000  0.300000
    y = tan(x)  :  0.000000  0.100335  0.202710  0.309336
    z = atan(y) :  0.000000  0.100000  0.200000  0.300000

### See also

sin(std::valarray) | applies the function std::sin to each element of valarray (function template)
cos(std::valarray) | applies the function std::cos to each element of valarray (function template)
atan(std::valarray) | applies the function std::atan to each element of valarray (function template)
tantanftanl (C++11)(C++11) | computes tangent (\({\small\tan{x}}\)tan(x)) (function)
tan(std::complex) | computes tangent of a complex number (\({\small\tan{z}}\)tan(z)) (function template)

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