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We can build a skew-symmetric matrix from a vector $v$ using formula

$$S(v) = \begin{pmatrix} v \times i \ \ v \times j \ \ v \times k \end{pmatrix}$$ where $i,j,k$ are vectors of the standard basis.

But how to obtain vector $v$ from its skew-symetric matrix?

Is there any linear formula for that ?

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**AFTER 2 hours**

I think I have found solution:

$$v=-ij^TS(v)k-jk^TS(v)i-ki^TS(v)j$$

Thank you for discussion.

**AFTER 20 hours**

I have one **additional question:**

could $v$ be calculated with one formula also from $S^2(v)$ ?

**AFTER 31 hours**

It seems it’s hard to obtain straightforward formula.

$v$ can be obtained from $S^2(v)=vv^T-v^TvI$ but by a rather tedious analysis.

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Let $v=(x,y,z)^\top$

Then

$v\times i = (0, z,-y)^\top$

$v\times j = (-z, 0,x)^\top$

$v\times k = (y, -x,0)^\top$

This means that $S(v) = \begin{pmatrix}0&-z&y\\z&0&-x\\-y&x&0\end{pmatrix}$

Now you can easily see the components of $v$

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