In Mathcad Prime 3.1 has come out this inexplicable error. How to correct it?

[-MFra-]

Hi all

In Mathcad Prime 3.1 has come out this inexplicable error. How to correct it? it is enclosed in the box in black, of the following figure.

Thk.

[LucMeekes · Accepted solution]

In your definition of F.s, and its usage in the three partial deriatives, each x, y and z are explicitly labelled as 'variable' but the variable to differentiate to (the x, y and z in dx, dy and dz) are 'automatic'. This may make the variable to differentiate to different from the arguments to the F.s function, hence they are treated as constants.

If you change the x, y and z in dx, dy and dz respectively to label type 'variable' it should work.

In the lowest box all x y and z are 'automatic', so that works as expected.

Luc

[-MFra-]

Hi Luc

Yes, by changing the labels of x, y, z, from a variable to automatic, it works.

Thk

[DJF]

Luc is on the right track.  However, setting everything to variable didn't seem to solve it.  But If I just retype it everything it seems to work.   So, however you entered the a,b,c as 'constants' seems to be messing up.  (I recently posted a thread where it was found symbolics automatically reverted to constants instead of defined variables (c = speed of light).  Not sure if this could be related.)