Please how do I compute the div n,  (n.curl n), (n.curl n)^2 and (n x curl n) and  (n x curl n)^2 given the information below: 

restart; restart; with(VectorCalculus); with(LinearAlgebra);

I.e.,

n = (cos(theta(x,y), sin(theta(x,y), 0).

I tried 

divn := Divergence(proc (x, y, z) options operator, arrow; `<,>`(n) end proc);

but received: Error, (in VectorCalculus:-Divergence) the procedure must evaluate to a Vector

Please why does 

roots(x^5 - C__1*x^4 -C__2*x^3 -C__3*x^2 -C__4*x +C__5, x);

returns  [ ]?

Please how  can I use getdata to extract only 200x2 of 208x2 matrix from maple to excel.

For instance I have:

Q:= ( seq( seq( plottools:-getdata(ans1[s1,3])[j,3],j=1..3), s1=1));

It returns  208x2,  200x2 200x2 matrices and I can't extract it using 

`<|>`( seq( seq( plottools:-getdata(ans1[s1,3])[j,3],j=1..3), s1=1));

because the matrices have different dimension. Please, how can make 208x2 matrix to 200x2?

Hi, please how do I delete only the 0*I of the complex expression: 0.*I - 3?

I tried this:  remove(`=`, [0.*I-3, 5, 7, -2], 0.*I);

But couldn't work.

Please, how do I generate a list of ones in maple?