Unrecognized function or variable 'zvar'.

[John D'Errico]

No reason to ask the same identical question twice. I closed your other question.

Answer 1

[VBBV]

xlabel('xvar')
ylabel('yvar')
xlabel('zvar')

If zvar, yvar and xvar are strings or numeric values passed to function viewSolid, then you must define them before. But it seems they are titles for plot axes, so put them in quotes.

[VBBV]

May be you mean

>>viewSolid(var(1),F, G, var(2), f,g,var(3), a,b)

var may be vector of values containing the z,y and x values

[Varshini]

Yet doesn't work

[VBBV]

What is not working ? Can you show what is error you get? All text in red color

[Varshini]

[VBBV]

The picture you attach is not clear. But it seems that xvar , yvar and zvar are symbolic variables or strings. So you need to pass them to function in double quotes

>>viewSolid("zvar",F, G, "yvar", f,g,"xvar", a,b)

[Stephen23]

Indexing is never valid in a function signature, so the function you show will not work.

None of the "viewSolid" functions I found during a quick web search had indexing in the function signature.