Hi to all, I create a composed function, but I don't understand what is wrong.
Please help

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I attach the file to clarify the problem

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2spline.sm (26,73 KiB) scaricato 1312 volta(e).

When defining a1, b1, c1.. etc, you define them as rows of a matrix (notice how they are still in parenthesis), and they remain a single entry matrix. This causes an error later on since you can't take a derivative of a matrix.

Instead of extracting the row, extract the element by using the "el" function, or write the matrix name followed by "[" and the row number.

eg. a.1 : M[1

The cases() function helps a lot in writing piecewise continuous functions in a readable way.

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2spline_Kr.sm (23,73 KiB) scaricato 1349 volta(e).

Hi, Ernesto and Martin.
Thank you for your help.
I'm new to the use of smath studio. I understand my mistake....It's a mathematical error!
Now I have istalled the Function extension.
Bye
Davide