Using Maple to find the normal vector

Question

I'm trying to find the normal vector to the level surface $xyz = 1$ at an arbitrary point $(a, b, c)$

with(Student[VectorCalculus]);
PrincipalNormal(PositionVector([x, y, 1/(x*y), x, y]));

Any idea what's wrong with my code? I keep getting "could not determine unique indeterminate: {x, y} "

I tried to read the documentation but the functions were given in parametric form.

Answer 1

You need to replace xy with x*y. Juxtaposition does not imply multiplication; rather, xy is treated as a distinct variable.