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[Merged by Bors] - chore: mark neg_div_neg_eq as simp #9332

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[Merged by Bors] - chore: mark neg_div_neg_eq as simp #9332

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61f3a11
chore: mark neg_div_neg_eq as simp
alexjbest Dec 29, 2023
58bd95d
fix nontermin
alexjbest Dec 29, 2023
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1 change: 1 addition & 0 deletions Mathlib/Algebra/Field/Basic.lean
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Expand Up @@ -118,6 +118,7 @@ theorem neg_div (a b : K) : -b / a = -(b / a) := by
theorem neg_div' (a b : K) : -(b / a) = -b / a := by simp [neg_div]
#align neg_div' neg_div'

@[simp]
theorem neg_div_neg_eq (a b : K) : -a / -b = a / b := by rw [div_neg_eq_neg_div, neg_div, neg_neg]
#align neg_div_neg_eq neg_div_neg_eq

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6 changes: 4 additions & 2 deletions Mathlib/NumberTheory/ModularForms/JacobiTheta/Basic.lean
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Expand Up @@ -100,9 +100,11 @@ theorem jacobiTheta_S_smul (τ : ℍ) :
rw [mul_comm ((1 : ℂ) / _) _, mul_one_div, eq_div_iff ha', mul_comm _ (_ ^ _), eq_comm] at this
have expo1 : ∀ n : ℤ, -↑π / (-I * ↑τ) * (n : ℂ) ^ 2 = ↑π * I * (n : ℂ) ^ 2 * (-↑τ)⁻¹ := by
intro n
field_simp [hτ, I_ne_zero]
simp only [neg_mul, neg_div_neg_eq, div_mul_eq_mul_div, inv_eq_one_div, mul_div_assoc', mul_one,
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Should this be viewed as a regression? Or is there an explanation why this simp only is morally the better proof?

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Before it was nonterminal so liable to break

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But I'm not sure we have a field simp only

ne_eq, neg_eq_zero, hτ, not_false_eq_true, eq_div_iff, I_ne_zero,
mul_ne_zero, div_eq_iff]
ring_nf
rw [I_sq, mul_neg, mul_one, neg_neg]
rw [I_sq, mul_neg, mul_one]
simp_rw [expo1] at this
have expo2 : ∀ n : ℤ, -↑π * (-I * ↑τ) * (n : ℂ) ^ 2 = ↑π * I * (n : ℂ) ^ 2 * ↑τ := by
intro n
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