English
If a,b ∈ Part α and ma ∈ a, mb ∈ b, then ma \ mb ∈ a \ b.
Русский
Если a и b — части α, ma ∈ a, mb ∈ b, тогда ma \ mb ∈ a \ b.
LaTeX
$$$$ [SDiff \alpha] (a,b : \mathrm{Part}(\alpha)) \ (ma,mb : \alpha) \ (ha : ma \in a) (hb : mb \in b) \Rightarrow ma \\ mb \in a \\ b. $$$$
Lean4
theorem sdiff_mem_sdiff [SDiff α] (a b : Part α) (ma mb : α) (ha : ma ∈ a) (hb : mb ∈ b) : ma \ mb ∈ a \ b := by
simp [sdiff_def]; aesop