(%i1) h : x1 ^ 2 + x2 ^ 2 ;

\[\operatorname{(h) }{{\ensuremath{\mathrm{x2}}}^{2}}+{{\ensuremath{\mathrm{x1}}}^{2}}\]

(%i2) dh : jacobian ( [ h ] , [ x1 , x2 , x3 ] ) ;

\[\operatorname{(dh) }\begin{pmatrix}2 \ensuremath{\mathrm{x1}} & 2 \ensuremath{\mathrm{x2}} & 0\end{pmatrix}\]

(%i3) D : nullspace ( dh ) ;

\[\]\[\mbox{Proviso:} \operatorname{notequal}\left( 2 \ensuremath{\mathrm{x1}}\operatorname{,}0\right) \]

\[\operatorname{(D) }\operatorname{span}\left( \begin{pmatrix}0\\ 0\\ -2 \ensuremath{\mathrm{x2}}\end{pmatrix}\operatorname{,}\begin{pmatrix}-2 \ensuremath{\mathrm{x2}}\\ 2 \ensuremath{\mathrm{x1}}\\ 0\end{pmatrix}\right) \]

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