diff --git a/Mathlib/LinearAlgebra/Projectivization/Independence.lean b/Mathlib/LinearAlgebra/Projectivization/Independence.lean index 8e265ee8a07369..03bf24b66cb6ed 100644 --- a/Mathlib/LinearAlgebra/Projectivization/Independence.lean +++ b/Mathlib/LinearAlgebra/Projectivization/Independence.lean @@ -112,4 +112,11 @@ theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := b theorem independent_pair_iff_ne (u v : ℙ K V) : Independent ![u, v] ↔ u ≠ v := by rw [independent_iff_not_dependent, dependent_pair_iff_eq u v] +/-- Two points are independent if and only if their underlying vectors are linearly independent. -/ +lemma independent_mk_iff_LinearIndependent {u v : V} (hu : u ≠ 0) (hv : v ≠ 0) : + Independent ![mk K u hu, mk K v hv] ↔ LinearIndependent K ![u, v] := by + rw [independent_pair_iff_ne, ne_eq, mk_eq_mk_iff' K u v hu hv, linearIndependent_fin2] + simp only [Matrix.cons_val_zero, Matrix.cons_val_one] + exact ⟨fun h ↦ ⟨hv, fun a ha ↦ h ⟨a, ha⟩⟩, fun ⟨_, h⟩ ⟨a, ha⟩ ↦ h a ha⟩ + end Projectivization