Issues with solve. Cannot solve symbolically. Returning a numeric approximation instead.

Hi there,

I'm trying to use 'solve' for 'a' by using 'syms' but I think it always retrieve an answer even if it didn't solve. I'm solving for a vector that is varying gradually so the 'aSolved' variable shall vary gradually but instead I have some points lying outside the range. I have some values in excel and I'm comparing them and for some values the results is exactly the same but in some other cases they are not. Here is where I called the 'solve:

for i=1:q
  syms a positive
  Ab=(a(i)g(i)).*(((m(i)*(1-cos(a)))-m(i))*(a) + m(i)*sin(a)) + g(i)*pi.*((m(i)*(1-cos(a)))-m(i))==0;
  solve_a=solve(eqn1,a);
  aSolved(i)=solve_a;
end

If anyone have any idea about what might be happening, I'll appreciate very much if you can give me some guidance on this.

Best, Martha

Answer 1

[Torsten]

As written, your equation reduces to

a(i)*(-cos(asol)*asol + sin(asol))-cos(asol)*pi==0

where I renamed the solution variable because of the equally named numeric array "a".

I suspect that the above equation might have several roots.

Best wishes

Torsten.