coefficients of differential equation defined by strings

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F R
F R 2018-4-30
编辑： F R 2018-4-30
I have a differential equation as string like
a*x1''[t] + b*cos(x2[t])*x1''[t] - n*x2'[t]*x1'[t]*sin(x2[t])-
c*(x2'[t])^2*sin(x2[t]) + g*cos(x1[t]) = In
and I want to extract the coefficients of
x1''[t], x1'[t], x2'[t]
and also extract the rest (which does not include any of these variables) as another term.
Is there a way to do it?
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Walter Roberson
Walter Roberson 2018-4-30
How do you want to handle the fact that you have x2'[t]^2 ? Do you want the coefficients for each power of each derivative ?
Analysis that needs to be able to handle (expression)^power and properly extract the coefficients of the variables by expansion, is not so easy to handle properly. Can we assume that the symbolic toolbox is present?
F R
F R 2018-4-30
编辑：F R 2018-4-30
I want to extract the coefficient of x2'[t], so it should return
-c*x2'[t]*sin(x2[t])
yes, any toolbox which can handle this in Matlab is appreciated

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