English
Let a, b, c be elements of a generalized co-Heyting algebra. Then a \\ c ≤ (a \\ b) ⊔ (b \\ c).
Русский
Пусть a, b, c — элементы обобщённой коейтинговой алгебры. Тогда a \\ c ≤ (a \\ b) ⊔ (b \\ c).
LaTeX
$$$ a \\\\setminus c \\\\le a \\\\setminus b \\\\vee b \\\\setminus c $$$
Lean4
theorem sdiff_triangle (a b c : α) : a \ c ≤ a \ b ⊔ b \ c :=
by
rw [sdiff_le_iff, sup_left_comm, ← sdiff_le_iff]
exact sdiff_sdiff_le.trans le_sup_sdiff