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| import OAI.Geometry.CylinderCovering.Angular.CubicAreaDefinitions | |
| import OAI.Geometry.CylinderCovering.Angular.Taylor | |
| import OAI.Geometry.CylinderCovering.Angular.Margins | |
| namespace OAI | |
| open Set MeasureTheory | |
| open scoped Interval | |
| noncomputable section | |
| namespace CylinderCovering.Cubic | |
| lemma profile_le_one {q : ℝ} (hq : |q| ≤ 1) : profile q ≤ 1 := by | |
| have hq2 : q ^ 2 ≤ 1 := by nlinarith [(abs_le.mp hq).1, (abs_le.mp hq).2] | |
| have hq4 : q ^ 4 ≤ 1 := by nlinarith [sq_nonneg (q ^ 2), sq_nonneg q] | |
| unfold profile | |
| linarith | |
| lemma areaDensity_identity (q : ℝ) : | |
| 2 * profile q - (((1 + q ^ 2) / 2) ^ 2 + 2 * q ^ 2) / 2 = | |
| areaDensity q := by | |
| unfold profile areaDensity | |
| ring | |
| lemma areaDensity_integral : | |
| (∫ q in (-1 : ℝ)..1, areaDensity q) = -(1 / 15 : ℝ) := by | |
| unfold areaDensity | |
| have h₁ : IntervalIntegrable (fun q : ℝ => -(1 / 8 : ℝ) - q ^ 2 / 4) | |
| volume (-1) 1 := by | |
| apply Continuous.intervalIntegrable | |
| fun_prop | |
| have h₂ : IntervalIntegrable (fun q : ℝ => 7 * q ^ 4 / 8) volume (-1) 1 := by | |
| apply Continuous.intervalIntegrable | |
| fun_prop | |
| have h₃ : IntervalIntegrable (fun q : ℝ => q ^ 2 / 4) volume (-1) 1 := by | |
| apply Continuous.intervalIntegrable | |
| fun_prop | |
| rw [intervalIntegral.integral_add h₁ h₂, | |
| intervalIntegral.integral_sub (continuous_const.intervalIntegrable _ _) h₃] | |
| rw [intervalIntegral.integral_div, intervalIntegral.integral_div, | |
| intervalIntegral.integral_const_mul, integral_pow, integral_pow, | |
| intervalIntegral.integral_const] | |
| norm_num | |
| lemma inverseSqrt_bounds {x : ℝ} (hx : 0 ≤ x) : | |
| 0 ≤ 1 / Real.sqrt (1 + x) ∧ | |
| 1 / Real.sqrt (1 + x) ≤ 1 ∧ | |
| |1 / Real.sqrt (1 + x) - 1| ≤ x / 2 := by | |
| let t := Real.sqrt (1 + x) | |
| have ht : 1 ≤ t := by | |
| dsimp [t] | |
| exact (Real.le_sqrt (by norm_num) (by linarith)).2 (by linarith) | |
| have ht0 : 0 < t := by linarith | |
| have ht2 : t ^ 2 = 1 + x := Real.sq_sqrt (by linarith) | |
| have hu : 1 / t ≤ 1 := (div_le_one ht0).2 ht | |
| have hl : 1 - x / 2 ≤ 1 / t := by | |
| apply (le_div_iff₀ ht0).2 | |
| have hfac : 0 ≤ (t - 1) ^ 2 * (t + 2) := | |
| mul_nonneg (sq_nonneg _) (by linarith) | |
| nlinarith only [hfac, ht2] | |
| change 0 ≤ 1 / t ∧ 1 / t ≤ 1 ∧ |1 / t - 1| ≤ x / 2 | |
| refine ⟨by positivity, hu, ?_⟩ | |
| rw [abs_of_nonpos (by linarith : 1 / t - 1 ≤ 0)] | |
| linarith | |
| theorem scalar_cubic_remainder {eps D A : ℝ} | |
| (he0 : 0 ≤ eps) (he1 : eps ≤ 1 / 2) | |
| (hD0 : 0 ≤ D) (hD1 : D ≤ 1) (hA0 : 0 ≤ A) (hA1 : A ≤ 3) : | |
| |(1 + eps ^ 2 * D + 100 * eps ^ 3) ^ 2 / | |
| Real.sqrt (1 + eps ^ 2 * A) - | |
| (1 + eps ^ 2 * (2 * D - A / 2))| ≤ 1600 * eps ^ 3 := by | |
| let d := eps ^ 2 * D + 100 * eps ^ 3 | |
| let x := eps ^ 2 * A | |
| let F := 1 / Real.sqrt (1 + x) | |
| have he2 : 0 ≤ eps ^ 2 := sq_nonneg eps | |
| have he3 : 0 ≤ eps ^ 3 := pow_nonneg he0 _ | |
| have he4 : 0 ≤ eps ^ 4 := pow_nonneg he0 _ | |
| have he32 : eps ^ 3 ≤ eps ^ 2 / 2 := by | |
| nlinarith only [mul_le_mul_of_nonneg_right he1 he2] | |
| have he43 : eps ^ 4 ≤ eps ^ 3 / 2 := by | |
| nlinarith only [mul_le_mul_of_nonneg_right he1 he3] | |
| have hd0 : 0 ≤ d := by dsimp [d]; positivity | |
| have hd : d ≤ 51 * eps ^ 2 := by | |
| dsimp [d] | |
| nlinarith only [mul_le_mul_of_nonneg_left hD1 he2, he32] | |
| have hx0 : 0 ≤ x := by dsimp [x]; positivity | |
| have hx : x ≤ 3 * eps ^ 2 := by | |
| dsimp [x] | |
| nlinarith only [mul_le_mul_of_nonneg_left hA1 he2] | |
| have hx2 : x ^ 2 ≤ 9 * eps ^ 4 := by | |
| nlinarith only [mul_self_le_mul_self hx0 hx] | |
| have hd2 : d ^ 2 ≤ 2601 * eps ^ 4 := by | |
| nlinarith only [mul_self_le_mul_self hd0 hd] | |
| have hdx : d * x ≤ 153 * eps ^ 4 := by | |
| nlinarith only [mul_le_mul hd hx hx0 (by positivity : 0 ≤ 51 * eps ^ 2)] | |
| obtain ⟨hF0, hF1, hFd⟩ := inverseSqrt_bounds hx0 | |
| change 0 ≤ F at hF0 | |
| change F ≤ 1 at hF1 | |
| change |F - 1| ≤ x / 2 at hFd | |
| have hR : |F - (1 - x / 2)| ≤ (3 / 8) * x ^ 2 := | |
| AngularTaylor.inv_sqrt_remainder hx0 | |
| have hcross : |2 * d * (F - 1)| ≤ d * x := by | |
| rw [abs_mul, abs_of_nonneg (by positivity : 0 ≤ 2 * d)] | |
| nlinarith only [mul_le_mul_of_nonneg_left hFd (by positivity : 0 ≤ 2 * d)] | |
| have hquad : |d ^ 2 * F| ≤ d ^ 2 := by | |
| rw [abs_of_nonneg (mul_nonneg (sq_nonneg d) hF0)] | |
| exact mul_le_of_le_one_right (sq_nonneg d) hF1 | |
| have hid : (1 + eps ^ 2 * D + 100 * eps ^ 3) ^ 2 / | |
| Real.sqrt (1 + eps ^ 2 * A) - (1 + eps ^ 2 * (2 * D - A / 2)) = | |
| (F - (1 - x / 2)) + 2 * d * (F - 1) + d ^ 2 * F + 200 * eps ^ 3 := by | |
| dsimp [F, x, d] | |
| ring | |
| rw [hid] | |
| have hab := abs_add_le (F - (1 - x / 2)) (2 * d * (F - 1)) | |
| have habc := abs_add_le ((F - (1 - x / 2)) + 2 * d * (F - 1)) (d ^ 2 * F) | |
| have habcd := abs_add_le ((F - (1 - x / 2)) + 2 * d * (F - 1) + d ^ 2 * F) | |
| (200 * eps ^ 3) | |
| rw [abs_of_nonneg (by positivity : 0 ≤ 200 * eps ^ 3)] at habcd | |
| nlinarith only [hab, habc, habcd, hR, hcross, hquad, hx2, hd2, hdx, he43, he3] | |
| lemma coefficient_bounds {a b : ℝ} (ha : |a| ≤ 1) (hb : |b| ≤ 1) : | |
| 0 ≤ alpha a b ∧ alpha a b ≤ 1 ∧ |beta a b| ≤ 1 ∧ | |
| 0 ≤ profileMax a b ∧ profileMax a b ≤ 1 ∧ | |
| 0 ≤ speedSq a b ∧ speedSq a b ≤ 3 := by | |
| have hab : |a * b| ≤ 1 := by | |
| rw [abs_mul] | |
| exact (mul_le_mul ha hb (abs_nonneg _) (by norm_num)).trans_eq (by norm_num) | |
| have hsum : |a + b| ≤ 2 := (abs_add_le a b).trans (by linarith) | |
| have ha0 : 0 ≤ alpha a b := by | |
| unfold alpha | |
| linarith [(abs_le.mp hab).1] | |
| have ha1 : alpha a b ≤ 1 := by | |
| unfold alpha | |
| linarith [(abs_le.mp hab).2] | |
| have hb1 : |beta a b| ≤ 1 := by | |
| unfold beta | |
| rw [abs_div] | |
| norm_num | |
| linarith | |
| have hM0 : 0 ≤ profileMax a b := | |
| (profile_nonneg a).trans (le_max_left _ _) | |
| have hM1 : profileMax a b ≤ 1 := max_le (profile_le_one ha) (profile_le_one hb) | |
| refine ⟨ha0, ha1, hb1, hM0, hM1, ?_, ?_⟩ | |
| · unfold speedSq | |
| positivity | |
| · have ha2 : alpha a b ^ 2 ≤ 1 := by nlinarith only [ha0, ha1] | |
| have hb2 : beta a b ^ 2 ≤ 1 := by | |
| nlinarith only [(abs_le.mp hb1).1, (abs_le.mp hb1).2] | |
| unfold speedSq | |
| linarith | |
| lemma profile_lipschitz {a q : ℝ} (ha : |a| ≤ 1) (hq : |q| ≤ 1) : | |
| |profile a - profile q| ≤ 3 * |a - q| := by | |
| have ha2 : a ^ 2 ≤ 1 := by nlinarith only [(abs_le.mp ha).1, (abs_le.mp ha).2] | |
| have hq2 : q ^ 2 ≤ 1 := by nlinarith only [(abs_le.mp hq).1, (abs_le.mp hq).2] | |
| have hsum : |a + q| ≤ 2 := (abs_add_le a q).trans (by linarith) | |
| have hpoly : |1 + a ^ 2 + q ^ 2| ≤ 3 := by | |
| rw [abs_of_nonneg (by positivity : 0 ≤ 1 + a ^ 2 + q ^ 2)] | |
| linarith | |
| have hid : profile a - profile q = (a - q) * (a + q) * (1 + a ^ 2 + q ^ 2) / 2 := by | |
| unfold profile | |
| ring | |
| rw [hid, abs_div, abs_mul, abs_mul] | |
| norm_num | |
| have hmul := mul_le_mul hsum hpoly (abs_nonneg _) (by norm_num : (0 : ℝ) ≤ 2) | |
| have hfinal := mul_le_mul_of_nonneg_left hmul (abs_nonneg (a - q)) | |
| nlinarith only [hfinal] | |
| lemma profileMax_error {a b q : ℝ} (ha : |a| ≤ 1) (hb : |b| ≤ 1) | |
| (hqa : a ≤ q) (hqb : q ≤ b) : | |
| |profileMax a b - profile q| ≤ 3 * (b - a) := by | |
| have hq := abs_le_of_interval ha hb hqa hqb | |
| have h₁ := profile_lipschitz ha hq | |
| have h₂ := profile_lipschitz hb hq | |
| rw [abs_of_nonpos (by linarith : a - q ≤ 0)] at h₁ | |
| rw [abs_of_nonneg (by linarith : 0 ≤ b - q)] at h₂ | |
| have hlo : profile q ≤ profileMax a b := profile_le_max_endpoints hqa hqb | |
| rw [abs_of_nonneg (sub_nonneg.mpr hlo)] | |
| have hupper : profileMax a b ≤ profile q + 3 * (b - a) := by | |
| apply max_le | |
| · linarith [(abs_le.mp h₁).2] | |
| · linarith [(abs_le.mp h₂).2] | |
| linarith | |
| lemma square_error {x y e : ℝ} (hx : |x| ≤ 1) (hy : |y| ≤ 1) | |
| (hxy : |x - y| ≤ e) : |x ^ 2 - y ^ 2| ≤ 2 * e := by | |
| have hsum : |x + y| ≤ 2 := (abs_add_le x y).trans (by linarith) | |
| have he : 0 ≤ e := (abs_nonneg _).trans hxy | |
| calc | |
| |x ^ 2 - y ^ 2| = |x - y| * |x + y| := by rw [← abs_mul]; congr 1; ring | |
| _ ≤ e * 2 := mul_le_mul hxy hsum (abs_nonneg _) he | |
| _ = 2 * e := by ring | |
| lemma density_error {a b q : ℝ} (ha : |a| ≤ 1) (hb : |b| ≤ 1) | |
| (hqa : a ≤ q) (hqb : q ≤ b) : | |
| |2 * profileMax a b - speedSq a b / 2 - areaDensity q| ≤ 8 * (b - a) := by | |
| have hq := abs_le_of_interval ha hb hqa hqb | |
| have hc := coefficient_bounds ha hb | |
| have hα := alpha_error ha hq hqa hqb | |
| have hβ := beta_error hqa hqb | |
| have hq2 : q ^ 2 ≤ 1 := by nlinarith only [(abs_le.mp hq).1, (abs_le.mp hq).2] | |
| have hαq : |(1 + q ^ 2) / 2| ≤ 1 := by | |
| rw [abs_of_nonneg (by positivity : 0 ≤ (1 + q ^ 2) / 2)] | |
| linarith | |
| have hαabs : |alpha a b| ≤ 1 := by rw [abs_of_nonneg hc.1]; exact hc.2.1 | |
| have hαsq := square_error hαabs hαq hα | |
| have hβsq := square_error hc.2.2.1 hq hβ | |
| have hspeed : |speedSq a b - (((1 + q ^ 2) / 2) ^ 2 + 2 * q ^ 2)| ≤ 4 * (b - a) := by | |
| have hid : speedSq a b - (((1 + q ^ 2) / 2) ^ 2 + 2 * q ^ 2) = | |
| (alpha a b ^ 2 - ((1 + q ^ 2) / 2) ^ 2) + 2 * (beta a b ^ 2 - q ^ 2) := by | |
| unfold speedSq | |
| ring | |
| rw [hid] | |
| have hh := abs_add_le (alpha a b ^ 2 - ((1 + q ^ 2) / 2) ^ 2) | |
| (2 * (beta a b ^ 2 - q ^ 2)) | |
| rw [abs_mul] at hh | |
| norm_num at hh | |
| linarith | |
| have hM := profileMax_error ha hb hqa hqb | |
| have hid : 2 * profileMax a b - speedSq a b / 2 - areaDensity q = | |
| 2 * (profileMax a b - profile q) - | |
| (speedSq a b - (((1 + q ^ 2) / 2) ^ 2 + 2 * q ^ 2)) / 2 := by | |
| rw [← areaDensity_identity] | |
| ring | |
| rw [hid] | |
| have hh := abs_add_le (2 * (profileMax a b - profile q)) | |
| (-((speedSq a b - (((1 + q ^ 2) / 2) ^ 2 + 2 * q ^ 2)) / 2)) | |
| rw [← sub_eq_add_neg, abs_neg] at hh | |
| rw [abs_mul, abs_div] at hh | |
| norm_num at hh | |
| linarith | |
| lemma continuous_areaDensity : Continuous areaDensity := by | |
| unfold areaDensity | |
| fun_prop | |
| lemma interval_density_error {a b : ℝ} (ha : |a| ≤ 1) (hb : |b| ≤ 1) | |
| (hab : a ≤ b) : | |
| |(b - a) * (2 * profileMax a b - speedSq a b / 2) - | |
| (∫ q in a..b, areaDensity q)| ≤ 8 * (b - a) ^ 2 := by | |
| have hu : ∀ q ∈ Ι a b, | |
| ‖2 * profileMax a b - speedSq a b / 2 - areaDensity q‖ ≤ 8 * (b - a) := by | |
| intro q hq | |
| rw [Set.uIoc_of_le hab] at hq | |
| simpa only [Real.norm_eq_abs] using density_error ha hb hq.1.le hq.2 | |
| have h := intervalIntegral.norm_integral_le_of_norm_le_const hu | |
| rw [intervalIntegral.integral_sub | |
| (f := fun _ : ℝ => 2 * profileMax a b - speedSq a b / 2) | |
| (g := areaDensity) (continuous_const.intervalIntegrable _ _) | |
| (continuous_areaDensity.intervalIntegrable _ _), intervalIntegral.integral_const, | |
| Real.norm_eq_abs, smul_eq_mul, abs_of_nonneg (sub_nonneg.mpr hab)] at h | |
| nlinarith only [h] | |
| lemma count_mul_step {N : ℕ} (hN : 0 < N) : (N : ℝ) * step N = 2 := by | |
| have h := node_last hN | |
| dsimp [node] at h | |
| linarith only [h] | |
| def areaCoefficientSum (N : ℕ) : ℝ := ∑ j : Fin N, | |
| step N * (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2) | |
| lemma integral_mesh_sum {N : ℕ} (hN : 0 < N) : | |
| (∑ j : Fin N, ∫ q in node N j..node N (j + 1), areaDensity q) = -(1 / 15 : ℝ) := by | |
| rw [Fin.sum_univ_eq_sum_range | |
| (fun j : ℕ => ∫ q in node N j..node N (j + 1), areaDensity q) N] | |
| rw [intervalIntegral.sum_integral_adjacent_intervals | |
| (fun _ _ => continuous_areaDensity.intervalIntegrable _ _)] | |
| rw [node_zero, node_last hN, areaDensity_integral] | |
| lemma areaCoefficientSum_error {N : ℕ} (hN : 0 < N) : | |
| |areaCoefficientSum N + 1 / 15| ≤ 16 * step N := by | |
| have hi := integral_mesh_sum hN | |
| have hid : areaCoefficientSum N + 1 / 15 = | |
| ∑ j : Fin N, (step N * (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2) - | |
| ∫ q in node N j..node N (j + 1), areaDensity q) := by | |
| rw [Finset.sum_sub_distrib, hi] | |
| dsimp [areaCoefficientSum] | |
| ring | |
| rw [hid] | |
| calc | |
| _ ≤ ∑ j : Fin N, |step N * (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2) - | |
| ∫ q in node N j..node N (j + 1), areaDensity q| := | |
| Finset.abs_sum_le_sum_abs _ _ | |
| _ ≤ ∑ _j : Fin N, 8 * (step N) ^ 2 := by | |
| apply Finset.sum_le_sum | |
| intro j _ | |
| have hab : node N j ≤ node N (j + 1) := by | |
| have := node_succ N j | |
| have := step_pos hN | |
| linarith | |
| have h := interval_density_error (node_abs_le hN j.isLt.le) | |
| (node_abs_le hN (Nat.succ_le_of_lt j.isLt)) hab | |
| simpa only [node_succ] using h | |
| _ = 16 * step N := by | |
| simp only [Finset.sum_const, Finset.card_univ, Fintype.card_fin, nsmul_eq_mul] | |
| calc | |
| (N : ℝ) * (8 * (step N) ^ 2) = 8 * ((N : ℝ) * step N) * step N := by ring | |
| _ = 16 * step N := by rw [count_mul_step hN]; ring | |
| lemma areaTerm_remainder {eps a b : ℝ} (he0 : 0 ≤ eps) (he1 : eps ≤ 1 / 2) | |
| (ha : |a| ≤ 1) (hb : |b| ≤ 1) (hab : a ≤ b) : | |
| |areaTerm eps a b - (b - a) * (1 + eps ^ 2 * | |
| (2 * profileMax a b - speedSq a b / 2))| ≤ (b - a) * 1600 * eps ^ 3 := by | |
| rcases coefficient_bounds ha hb with ⟨_, _, _, hD0, hD1, hA0, hA1⟩ | |
| have h := scalar_cubic_remainder he0 he1 hD0 hD1 hA0 hA1 | |
| have hid : areaTerm eps a b - (b - a) * (1 + eps ^ 2 * | |
| (2 * profileMax a b - speedSq a b / 2)) = | |
| (b - a) * ((1 + eps ^ 2 * profileMax a b + 100 * eps ^ 3) ^ 2 / | |
| Real.sqrt (1 + eps ^ 2 * speedSq a b) - | |
| (1 + eps ^ 2 * (2 * profileMax a b - speedSq a b / 2))) := by | |
| unfold areaTerm cap | |
| ring | |
| rw [hid, abs_mul, abs_of_nonneg (sub_nonneg.mpr hab)] | |
| nlinarith only [mul_le_mul_of_nonneg_left h (sub_nonneg.mpr hab)] | |
| lemma areaSum_coefficient_remainder {eps : ℝ} {N : ℕ} | |
| (he0 : 0 ≤ eps) (he1 : eps ≤ 1 / 2) (hN : 0 < N) : | |
| |areaSum eps N - (2 + eps ^ 2 * areaCoefficientSum N)| ≤ 3200 * eps ^ 3 := by | |
| let f : Fin N → ℝ := fun j => step N * (1 + eps ^ 2 * | |
| (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2)) | |
| have hsum : (∑ j : Fin N, f j) = 2 + eps ^ 2 * areaCoefficientSum N := by | |
| dsimp [f, areaCoefficientSum] | |
| simp_rw [mul_add] | |
| rw [Finset.sum_add_distrib, Finset.mul_sum] | |
| have heq : (∑ j : Fin N, step N * (eps ^ 2 * | |
| (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2))) = | |
| ∑ j : Fin N, eps ^ 2 * (step N * | |
| (2 * profileMax (node N j) (node N (j + 1)) - | |
| speedSq (node N j) (node N (j + 1)) / 2)) := by | |
| apply Finset.sum_congr rfl | |
| intro j _ | |
| ring | |
| rw [heq] | |
| congr 1 | |
| simp only [mul_one, Finset.sum_const, Finset.card_univ, Fintype.card_fin, nsmul_eq_mul] | |
| exact count_mul_step hN | |
| rw [← hsum] | |
| unfold areaSum | |
| rw [← Finset.sum_sub_distrib] | |
| calc | |
| _ ≤ ∑ j : Fin N, |areaTerm eps (node N j) (node N (j + 1)) - f j| := | |
| Finset.abs_sum_le_sum_abs _ _ | |
| _ ≤ ∑ _j : Fin N, step N * 1600 * eps ^ 3 := by | |
| apply Finset.sum_le_sum | |
| intro j _ | |
| have hab : node N j ≤ node N (j + 1) := by | |
| have := node_succ N j | |
| have := step_pos hN | |
| linarith | |
| have h := areaTerm_remainder he0 he1 (node_abs_le hN j.isLt.le) | |
| (node_abs_le hN (Nat.succ_le_of_lt j.isLt)) hab | |
| simpa only [node_succ, f] using h | |
| _ = 3200 * eps ^ 3 := by | |
| simp only [Finset.sum_const, Finset.card_univ, Fintype.card_fin, nsmul_eq_mul] | |
| calc | |
| (N : ℝ) * (step N * 1600 * eps ^ 3) = ((N : ℝ) * step N) * 1600 * eps ^ 3 := by ring | |
| _ = 3200 * eps ^ 3 := by rw [count_mul_step hN]; ring | |
| theorem areaSum_expansion {eps : ℝ} {N : ℕ} | |
| (he0 : 0 ≤ eps) (he1 : eps ≤ 1 / 2) (hN : 0 < N) | |
| (hstep : step N ≤ eps ^ 2) : | |
| |areaSum eps N - (2 - eps ^ 2 / 15)| ≤ 3208 * eps ^ 3 := by | |
| have hR := areaSum_coefficient_remainder he0 he1 hN | |
| have hC := areaCoefficientSum_error hN | |
| have hc : |eps ^ 2 * (areaCoefficientSum N + 1 / 15)| ≤ 8 * eps ^ 3 := by | |
| rw [abs_mul, abs_of_nonneg (sq_nonneg _)] | |
| have h₁ := mul_le_mul_of_nonneg_left hC (sq_nonneg eps) | |
| have h₂ := mul_le_mul_of_nonneg_left hstep (by positivity : 0 ≤ 16 * eps ^ 2) | |
| have h₃ := mul_le_mul_of_nonneg_right he1 (pow_nonneg he0 3) | |
| nlinarith only [h₁, h₂, h₃] | |
| have hid : areaSum eps N - (2 - eps ^ 2 / 15) = | |
| (areaSum eps N - (2 + eps ^ 2 * areaCoefficientSum N)) + | |
| eps ^ 2 * (areaCoefficientSum N + 1 / 15) := by ring | |
| rw [hid] | |
| exact (abs_add_le _ _).trans (by linarith only [hR, hc]) | |
| end CylinderCovering.Cubic | |
| end | |
| end OAI | |