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Symbolic seems to have an error

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Stephen Wilkerson
Stephen Wilkerson on 11 Sep 2020
Closed: MATLAB Answer Bot on 20 Aug 2021
Two typos in my original post corrected
  2 Comments
John D'Errico
John D'Errico on 11 Sep 2020
Edited: John D'Errico on 11 Sep 2020
Then why did you feel the need to post it again? Just edit your original post. Anyway, it seems like everytime you don't understand a piece of code, you declare it to be a bug.
Stephen Wilkerson
Stephen Wilkerson on 11 Sep 2020
We'll do you have an answer?

Answers (3)

Stephen Wilkerson
Stephen Wilkerson on 11 Sep 2020
Yes that's what I ended up doing.

Stephen Wilkerson
Stephen Wilkerson on 11 Sep 2020
Now I'm unsure how to delete the second post?

Paul
Paul on 11 Sep 2020
Edited: Paul on 12 Sep 2020
The RHS of your differential equation should be 3*u.
In the frequency domain, Y(s) = H(s)*U(s). It looks like you're trying to get the step repsonse of your second order system, so U(s) = 1/s. You forgot to multiply by U(s) in your symbolic approach.
num = 3;
den = [1 2 5];
syms s
nums = poly2sym(num,s);
dens = poly2sym(conv(den,[1 0]),s); % here!
ilaplace(nums/dens)
ans =
3/5 - (3*exp(-t)*(cos(2*t) + sin(2*t)/2))/5

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