When expressions are entered into the interactive prover (as command parameters), take care to not introduce typing mistakes.
For example:
The following typing is correct: i ∈ℤ et E ∈ℤ.
The following typing is correct: E,F ∈ℤ ×ℤ.
The following typing is correct: b,e1,e2 ∈ℤ ×ℤ ×ℤ.
In general, a typing error will produce a ill-typed goal which will not be provable.