I would like to compute the product


where $E$, $F_i$, and $r_i$ represent arbitrary numbers whose notation makes sense in the general problem I am working on.

When I simply copy and paste the LaTex expression into Mathematica, I get some weird stuff which clearly is not the product.

What I am doing wrong?

str = "(e*s+r_{13})(F_{13}s)(F_{3}s+r_{3})(F_{2}s+r_{2})(F_{12}s+r_{12})(F_{1}s+r_{1})(F_{23}s+r_{23})";
ToExpression[str, TeXForm]

(*    s Subscript[F, 13] (s Subscript[F, 1] + Subscript[r, 1])
      (s Subscript[F, 2] + Subscript[r, 2]) (s Subscript[F, 3] + Subscript[r, 3])
      (s Subscript[F, 12] + Subscript[r, 12]) (e s + Subscript[r, 13])
      (s Subscript[F, 23] + Subscript[r, 23])                     *)
  • $\begingroup$ Can I further ask how to ask mathematica to only show the coefficients of s^3 terms in the product? $\endgroup$ – crystal_math Jan 9 at 14:35
  • $\begingroup$ Yes, with Coefficient[%, s^3]. $\endgroup$ – Roman Jan 9 at 14:57
  • $\begingroup$ Please note that I've modified the first term from Es to e*s because Es is a single symbol. $\endgroup$ – Roman Jan 9 at 15:02

You can remove the space from the pasted-in LaTeX expression so your $Es$, which was interpreted as $E s$, goes back to being $Es$.

Expression as pasted in:


which evaluates to:


Edit the expression to:


so it now evaluates to:


which is what I presume you want.


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