# std::cosh(std::valarray)

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< cpp‎ | numeric‎ | valarray

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

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

### Parameters

va | - | value array to apply the operation to

### Return value

Value array containing hyperbolic cosine of the values in va.

### Notes

Unqualified function (cosh) is used to perform the computation. If such function is not available, std::cosh 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> cosh(const valarray<T>& va)
    {
        valarray<T> other = va;
        for (T& i : other)
            i = cosh(i);

        return other; // proxy object may be returned
    }

### Example

Run this code

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

    void show(const char* title, const std::valarray<float>& data)
    {
        const int w{9};
        std::cout << std::setw(w) << title << " | ";
        for (float x : data)
            std::cout << std::setw(w) << x << " | ";
        std::cout << '\n';
    }

    int main()
    {
        const std::valarray<float> x{.1, .2, .3, .4};
        const auto sinh = std::sinh(x);
        const auto cosh = std::cosh(x);
        const auto z = (cosh * cosh) - (sinh * sinh);

        show("x", x);
        show("sinh(x)", sinh);
        show("cosh(x)", cosh);
        show("z", z);
    }

Output:

            x |       0.1 |       0.2 |       0.3 |       0.4 |
      sinh(x) |  0.100167 |  0.201336 |   0.30452 |  0.410752 |
      cosh(x) |     1.005 |   1.02007 |   1.04534 |   1.08107 |
            z |         1 |         1 |         1 |         1 |

### See also

sinh(std::valarray) | applies the function std::sinh to each element of valarray (function template)
tanh(std::valarray) | applies the function std::tanh to each element of valarray (function template)
coshcoshfcoshl (C++11)(C++11) | computes hyperbolic cosine (\({\small\cosh{x}}\)cosh(x)) (function)
cosh(std::complex) | computes hyperbolic cosine of a complex number (\({\small\cosh{z}}\)cosh(z)) (function template)

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