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\htext (2.31 -2.83){$s_k$}
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\htext (1.80 -1.80){$\ddots$}
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\htext (3.34 -3.34){$A_{k+1}$}
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%begin textrectangle
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\htext (1.29 -3.34){$\Large \boldsymbol{0}$}
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%%\left( Q^{(k)}\right)^T

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%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%
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