theorem
proved
tactic proof
smul_mem_Radical
show as:
view Lean formalization →
formal statement (Lean)
54theorem smul_mem_Radical {n : ℕ} (α : Vec n) {v : Vec n} (s : ℝ)
55 (hv : v ∈ Radical α) :
56 s • v ∈ Radical α := by
proof body
Tactic-mode proof.
57 unfold Radical dot at hv ⊢
58 calc
59 ∑ i : Fin n, α i * (s * v i)
60 = s * ∑ i : Fin n, α i * v i := by
61 rw [Finset.mul_sum]
62 apply Finset.sum_congr rfl
63 intro i hi
64 ring
65 _ = 0 := by rw [hv]; ring
66