Hessian(f, t) コマンドは、t 内の変数に関する関数 f の  行列を計算します。これは、diff(f, t[i], t[j]) を (i, j) 成分に持つ行列となります。

with(VectorCalculus):

Warning, the assigned names <,> and <|> now have a global
binding
Warning, these protected names have been redefined and
unprotected: *, +, ., Vector, diff, int, limit, series

Hessian( cos(x*y), [x,y] );

Hessian( 1/(x^2+y^2+z^2), [x,y,z] );

H := unapply( %, [x,y,z] ):
H( 0.3, 0.7, 0.1 );