eig(a,b) matlab symbolic

조회 수: 3(최근 30일)
mohamdi mohamed
mohamdi mohamed 2023년 3월 17일
댓글: Sam Chak 2023년 4월 18일
hi, need some help
How do you find the eigenvalues of 2 symbolic matrix in Matlab?
i have this:
syms k1 k2 kx m1 m2 W
K = [ k1 + kx -kx 0
-kx k2 + kx -k2
0 -k2 k2]
M =[ 2*m1 0 0
0 2*m2 m2
0 m2 2*m2]
it retun me
Error using sym/eig
Too many input arguments.
but when i give value to k1 k2 m1 m2 its work
i need D with symbolic value some one can help me please

채택된 답변

Sam Chak
Sam Chak 2023년 3월 17일
Are you looking for the analytical solution like this?
syms k1 k2 kx m1 m2
K = [k1+kx -kx 0;
-kx k2+kx -k2;
0 -k2 k2]
K = 
M =[2*m1 0 0;
0 2*m2 m2;
0 m2 2*m2]
M = 
[V, Lambda] = eig(M*inv(K))
V = 
Lambda = 
  댓글 수: 4
Sam Chak
Sam Chak 2023년 4월 18일
Since you asked for a symbolical solution for eigenvalues, then that's the one produced by MATLAB eig() function that requires solving 3rd-degree polynomial equation. A 3rd-degree polynomial has analytical solutions. However, because there are many other parameters in the matrices, the given solution looks complicated.
I think the solution is already in the simplest form, as I don't find any terms that can be cancelled out or reducible. If you wish to solve it by hand, please look up Cardano's formula.

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mohamdi mohamed
mohamdi mohamed 2023년 3월 17일
i find this way
Dyn= M*inv(K)

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