English
For any N, Nontrivial N is equivalent to N ≠ ⊥.
Русский
Для любого N: ненулевой эквивалентен N ≠ ⊥.
LaTeX
$$Nontrivial N \\iff N \\neq ⊥$$
Lean4
theorem nontrivial_iff_ne_bot {N : LieSubmodule R L M} : Nontrivial N ↔ N ≠ ⊥ :=
by
constructor <;> contrapose!
· rintro rfl
by_contra! h;
rcases h with ⟨⟨m₁, h₁ : m₁ ∈ (⊥ : LieSubmodule R L M)⟩, ⟨m₂, h₂ : m₂ ∈ (⊥ : LieSubmodule R L M)⟩, h₁₂⟩
simp [(LieSubmodule.mem_bot _).mp h₁, (LieSubmodule.mem_bot _).mp h₂] at h₁₂
· rw [LieSubmodule.eq_bot_iff]
rintro ⟨h⟩ m hm
simpa using h ⟨m, hm⟩ ⟨_, N.zero_mem⟩