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Matlab fail to found symbolic equation system solution, why?
Posted:
Jun 28, 2013 6:39 PM


Dear friends,
I need help to solve a symbolic equation system, four equations and four variables, seems simple, but does not work. See the code:
%Declare 4 real symbolic variables ... syms('a0','real','a1','real','a2','real','a3','real');
%Declara the symbolic 2x2 matrix R ... R = ... [exp(a0*i)*exp((a1*i)/2)*exp((a3*i)/2)*(exp((a2*i)/2)/2 + exp((a2*i)/2)/2), ... exp(a0*i)*exp((a1*i)/2)*exp((a3*i)/2)*((exp((a2*i)/2)*i)/2  (exp((a2*i)/2)*i)/2); ... exp(a0*i)*exp((a1*i)/2)*exp((a3*i)/2)*((exp((a2*i)/2)*i)/2  (exp((a2*i)/2)*i)/2), ... exp(a0*i)*exp((a1*i)/2)*exp((a3*i)/2)*(exp((a2*i)/2)/2 + exp((a2*i)/2)/2)];
%Generating a sample matrix L ... L = subs(R, [a0 a1 a2 a3], [pi/7 pi/5 pi/3 pi])
L = 0.1162  0.8582i 0.0671  0.4955i 0.3455  0.3614i 0.5985 + 0.6260i
However, the matlab does not found solution to R == L, see:
>> solve(R == L) Warning: Explicit solution could not be found. > In solve at 169 ans = [ empty sym ]
Why the solution [pi/7 pi/5 pi/3 pi] isn't found? How do it correctly?
Best regards, Fernando



