# Getting the real part of a expression

I'm trying to get the real part of a expression, but I failed. It looks like this.

Does anyone have a solution?

By the way, it is quite weird because when I simplify this:

Mathematica returns the right answer, but I can't tell the big difference between the two expressions.

Here is my code:

vectorVr = Array[Subscript[vr, #] &, 9];
vectorVi = Array[Subscript[vi, #] &, 9];
$Assumptions = Join[vectorVr, vectorVi] ∈ Reals; FullSimplify[ (0. + 0.0576 I) (I Subscript[vi, 1] - I Subscript[vi, 4] + Subscript[vr, 1] - Subscript[vr, 4]) (-I Subscript[vi, 1] + I Subscript[vi, 4] + Subscript[vr, 1] - Subscript[vr, 4]) // Expand // Re]  ## 1 Answer vectorVr = Array[Subscript[vr, #] &, 9]; vectorVi = Array[Subscript[vi, #] &, 9];$Assumptions = Join[vectorVr, vectorVi] \[Element] Reals;

(0. + 0.0576 I) (I Subscript[vi, 1] - I Subscript[vi, 4] +
Subscript[vr, 1] - Subscript[vr, 4]) (-I Subscript[vi, 1] +
I Subscript[vi, 4] + Subscript[vr, 1] - Subscript[vr, 4]) //
ComplexExpand // Re // Simplify

(*  0  *)