lean_workbook_plus_20623

Proved

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

If $a\geq -b$ , then $-a\leq b$ , combining this with $b\leq a$ you get $-a\leq b\leq a$ , i.e. $a\geq |b|$ .

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_20623  (a b : ℝ)
  (h₀ : -b ≤ a)
  (h₁ : b ≤ a) :
  a ≥ |b|   :=  by sorry

Source