Questing about symbolic differentiation, inner derivative

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Per
Per 2014-2-5
评论： Walter Roberson 2014-2-5
Hi everybody,
I am doing a project that requires alot of symbolic differentiation. I need to differentiate expression like cos(theta(t)) w.r.t t, is this possible with matlab? If so, how?
I know that I could easily do this with mathematica but I am also using simulink, so it would be easier just to use one software.
BR,
Per

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采纳的回答

Walter Roberson
Walter Roberson 2014-2-5
Yes, the Symbolic Toolbox can handle that without difficulty. The syntax would go something like
syms theta(t) t
diff(cos(theta(t))

更多回答（1 个）

Per
Per 2014-2-5
Walter,
Thank you for the fast answer. Can I extend this syntax to vectors of symbols?
BR,
Per
  1 个评论
Walter Roberson
Walter Roberson 2014-2-5
See http://www.mathworks.com/help/symbolic/diff.html
You can differentiate a vector of expressions, but you cannot differentiate with respect to a vector. If what you are looking for is the partial derivatives then you can use the syntax
diff(F,var1,...,varN) differentiates F with respect to the variables var1,...,varN.
but you cannot use diff(f,[var1, var2, var3... varn])
What you can do in MATLAB is
varvec = [var1, var2, var3... varn]; %however it got built
T = num2cell(varvec); %convert to cell array
diff(F, T{:})
the T{:} syntax expands the cell array to become individual arguments to the call.

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