AlexKontorovich/PrimeNumberTheoremAnd
Source indexedlemma · leanprover/lean4:v4.32.0
x_log_x_atTop
PrimeNumberTheoremAnd.Consequences · PrimeNumberTheoremAnd/Consequences.lean:1332 to 1348
Mathematical statement
Exact Lean statement
lemma x_log_x_atTop : Filter.Tendsto (fun x => x / Real.log x) Filter.atTop Filter.atTop
Complete declaration
Lean source
Full Lean sourceLean 4
lemma x_log_x_atTop : Filter.Tendsto (fun x => x / Real.log x) Filter.atTop Filter.atTop := by have inv_log_x_div := Filter.Tendsto.comp (f := fun x => Real.log x / x) (g := fun x => x⁻¹) (x := Filter.atTop) (y := (nhdsWithin 0 (Set.Ioi 0))) (z := Filter.atTop) ?_ ?_ · simp_rw [Function.comp_def, inv_div] at inv_log_x_div exact inv_log_x_div · exact tendsto_inv_nhdsGT_zero (𝕜 := ℝ) · rw [tendsto_nhdsWithin_iff] refine ⟨?_, ?_⟩ · have log_div_x := Real.tendsto_pow_log_div_mul_add_atTop 1 0 1 (by simp) simp only [pow_one, one_mul, add_zero] at log_div_x exact log_div_x · simp only [Set.mem_Ioi, eventually_atTop] use 2 intro x hx have log_pos: 0 < Real.log x := by refine (Real.log_pos_iff ?_).mpr ?_ <;> linarith positivity