# std::atan2(std::valarray)

< cpp‎ | numeric‎ | valarray

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Defined in header `<valarray>`
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template< class T >
valarray<T> atan2( const valarray<T>& y, const valarray<T>& x );
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<td > (1) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

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template< class T >
valarray<T> atan2( const valarray<T>& y, const T& vx );
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<td > (2) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

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template< class T >
valarray<T> atan2( const T& vy, const valarray<T>& x );
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<td > (3) </td> <td class="t-dcl-nopad"> </td> </tr> Template:ddcl list end

Computes the inverse tangent of `y/x` using the signs of arguments to correctly determine quadrant.

1) Computes the inverse tangent of each pair of corresponding values from `y` and `x`.

The behavior is undefined if x.size() != y.size().

2) Computes the inverse tangent of `vx` and each value in the numeric array `y`.
3) Computes the inverse tangent of `vy` and each value in the numeric array `x`.

## Contents

### Parameters

 x, y - numeric arrays to compute inverse tangent of vy, vx - values to compute inverse tangent of

### Return value

A numeric array containing the results of computation of inverse tangent.

### Notes

Unqualified function (atan2) is used to perform the computation. If such function is not available, std::atan2 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: