-- File: optlib/Optlib/Algorithm/GD/GradientDescentStronglyConvex.lean
Theorem statement:
theorem extracted_formal_statement_84.{u_1} {E : Type u_1} [inst : NormedAddCommGroup E] [inst_1 : InnerProductSpace ℝ E]
  [inst_2 : CompleteSpace E] {f : E → ℝ} {m : ℝ} {f' : E → E} {xm x₀ : E} {alg : Gradient_Descent_fix_stepsize f f' x₀}
  (hm : m > 0) (min : IsMinOn f univ xm)
  (step₂ : Gradient_Descent_fix_stepsize.a f f' x₀ ≤ 2 / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)))
  (hsc : StrongConvexOn univ m f) (this_1 : LipschitzWith (Gradient_Descent_fix_stepsize.l f f' x₀) f')
  (this_2 : ↑(Gradient_Descent_fix_stepsize.l f f' x₀) > 0)
  (reduction :
    ∀ (k : ℕ),
      ‖Gradient_Descent_fix_stepsize.x f f' x₀ (k + 1) - xm‖ ^ 2 ≤
        (1 -
            Gradient_Descent_fix_stepsize.a f f' x₀ *
              (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀) / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)))) *
          ‖Gradient_Descent_fix_stepsize.x f f' x₀ k - xm‖ ^ 2)
  (this : 0 < m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀))
  (h_original_goal :
    0 ≤
      (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
          Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀))) /
        (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀))) :
  0 ≤
        m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
          Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀)) ∧
      0 ≤ m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) ∨
    m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
          Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀)) ≤
        0 ∧
      m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) ≤ 0 := sorry

Tactic state before:
E : Type u_1
inst✝² : NormedAddCommGroup E
inst✝¹ : InnerProductSpace ℝ E
inst✝ : CompleteSpace E
f : E → ℝ
m : ℝ
f' : E → E
xm x₀ : E
alg : Gradient_Descent_fix_stepsize f f' x₀
hm : m > 0
min : IsMinOn f univ xm
step₂ : Gradient_Descent_fix_stepsize.a f f' x₀ ≤ 2 / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀))
hsc : StrongConvexOn univ m f
this✝¹ : LipschitzWith (Gradient_Descent_fix_stepsize.l f f' x₀) f'
this✝ : ↑(Gradient_Descent_fix_stepsize.l f f' x₀) > 0
reduction :
  ∀ (k : ℕ),
    ‖Gradient_Descent_fix_stepsize.x f f' x₀ (k + 1) - xm‖ ^ 2 ≤
      (1 -
          Gradient_Descent_fix_stepsize.a f f' x₀ *
            (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀) / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)))) *
        ‖Gradient_Descent_fix_stepsize.x f f' x₀ k - xm‖ ^ 2
this : 0 < m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)
⊢ 0 ≤
    (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
        Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀))) /
      (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀))

Tactic: rw [div_nonneg_iff]

Tactic state after:
[E : Type u_1
 inst✝² : NormedAddCommGroup E
 inst✝¹ : InnerProductSpace ℝ E
 inst✝ : CompleteSpace E
 f : E → ℝ
 m : ℝ
 f' : E → E
 xm x₀ : E
 alg : Gradient_Descent_fix_stepsize f f' x₀
 hm : m > 0
 min : IsMinOn f univ xm
 step₂ : Gradient_Descent_fix_stepsize.a f f' x₀ ≤ 2 / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀))
 hsc : StrongConvexOn univ m f
 this✝¹ : LipschitzWith (Gradient_Descent_fix_stepsize.l f f' x₀) f'
 this✝ : ↑(Gradient_Descent_fix_stepsize.l f f' x₀) > 0
 reduction :
   ∀ (k : ℕ),
     ‖Gradient_Descent_fix_stepsize.x f f' x₀ (k + 1) - xm‖ ^ 2 ≤
       (1 -
           Gradient_Descent_fix_stepsize.a f f' x₀ *
             (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀) / (m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)))) *
         ‖Gradient_Descent_fix_stepsize.x f f' x₀ k - xm‖ ^ 2
 this : 0 < m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀)
 ⊢ 0 ≤
         m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
           Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀)) ∧
       0 ≤ m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) ∨
     m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) -
           Gradient_Descent_fix_stepsize.a f f' x₀ * (2 * m * ↑(Gradient_Descent_fix_stepsize.l f f' x₀)) ≤
         0 ∧
       m + ↑(Gradient_Descent_fix_stepsize.l f f' x₀) ≤ 0]

Premises used:
div_nonneg_iff : ∀ {α : Type u_2} [inst : LinearOrderedField α] {a b : α}, 0 ≤ a / b ↔ 0 ≤ a ∧ 0 ≤ b ∨ a ≤ 0 ∧ b ≤ 0