Error using mupadengin​e/feval_in​ternal Arithmetical expression expected.

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]);

[Walter Roberson]

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]

We would have to know the value of the various variables. I suspect one or more of them are not numeric.

Answer 1

[Walter Roberson]

According to a previous thread, the problem is that one of the expressions generates NaN