lean_workbook_plus_34673

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

If $1>x \geq \frac{1}{2}$ then $abc \geq 0$ and our inequality becomes: \n\n

\frac{1+2x^2}{1-x^2}\geq 2

(true enough)

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_34673  (x : ℝ)
  (h₀ : 1 > x ∧ x ≥ 1 / 2) :
  (1 + 2 * x^2) / (1 - x^2) ≥ 2   :=  by sorry

Source