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.

You need one parenthesis , i.e. PrincipalNormal(PositionVector([x, y, 1/(xy), x, y])$\mathbf{\bigg)}$;. When you get that error it is because of incomplete parenthesis, or something similar. — Eff, Oct 14 '14 at 20:30
See https://www.mapleprimes.com/questions/132980-Surface-Normal-In-Vector-Calculus. — Leponzo, Aug 09 '20 at 19:02

score 0 · Answer 1 · answered Oct 14 '14 at 23:39

0

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

answered Oct 14 '14 at 23:39

Carl Love

Thanks, that fixed at least part of the problem. Now I'm getting "could not determine unique indeterminate: {x, y}" – Jack Oct 14 '14 at 23:43
1

As far as I can tell from the documentation, the command PricipalNormal is for curves, not surfaces. – Carl Love Oct 15 '14 at 05:11

1 Answers1