Error using mupadengine/feval_internal Arithmetical expression expected.

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yasin yalcin 2021-9-5

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https://ww2.mathworks.cn/matlabcentral/answers/1447104-error-using-mupadengine-feval_internal-arithmetical-expression-expected

回答： Walter Roberson 2025-5-6

67- syms a b

68- eqns=[delta_T==rho*4*pi*r(i)*V_inf^2*(1+a)*a*dr ,delta_Q==rho*4*pi*r(i)^3*V_inf*(1+a)*b*omg*dr];

69- S=vpasolve(eqns,[a b]);

Error using mupadengine/feval_internal

Arithmetical expression expected.

Error in sym/vpasolve (line 172)

sol = eng.feval_internal('symobj::vpasolve',eqns,vars,X0);

Error in untitled (line 69)

S=vpasolve(eqns,[a b]);

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Walter Roberson 2025-5-6

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Seems okay with a naive implementation.

syms a b
delta_T = rand();
rho = rand();
i = 1; r(i) = rand();
V_inf = rand();
dr = rand();
delta_Q = rand();
omg = rand();
eqns=[delta_T==rho*4*pi*r(i)*V_inf^2*(1+a)*a*dr ,delta_Q==rho*4*pi*r(i)^3*V_inf*(1+a)*b*omg*dr];
S=vpasolve(eqns,[a b])
S = struct with fields:
    a: [2x1 sym]
    b: [2x1 sym]