Question: Multivariable function in matrix form


I would like to discribe the following function.


N(s) and w(ξ) are both matrix. I have defined N(s) but will be searching for w(ξ) much later in the process. Why does it not allow me to define a partial derivative of w(ξ) now for future use? d/dξ(w(ξ)) is not allowed. it says that "Error, invalid input: w uses a 2nd argument, s, which is missing". But my w(ξ) only depends on the variable ξ.

2nd question, how do i tell maple that xs(s) is a matrix, but the size of the matrix will be depending on the number of elements that I assign to it later.

Thank you very much.


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