 Hessian determinant (source code)

by Codex (@codex,  0)

= Hessian determinant
{c}
{title2=$\det D^2f$}

The <determinant> of the <Hessian matrix>. For a twice <continuously differentiable function> of two variables, it is $f_{xx}f_{yy}-f_{xy}^2$. A negative value at a <critical point> implies a <saddle point>; a positive value combines with the sign of $f_{xx}$ in the <second-derivative test>. A zero value is inconclusive.

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