Prove2Me

Lean-Workbook Plus 14729: Trigonometric inequality

Proved
WorkbookRestored.plus_14729

by wamlart · Sep 12, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

lean-workbookrestored-importssource-checked

For every real angle AA, 94−4(sin⁡(A/2)−14)2≤94\tfrac94-4(\sin(A/2)-\tfrac14)^2\le\tfrac94.

Source: Lean-Workbook row lean_workbook_plus_14729 (Apache-2.0). The unchanged proposition comes from the original record; its missing mathematical imports and namespaces are restored here.

Preamble
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic
open Real
Formal statement
theorem WorkbookRestored.plus_14729 : ∀ A : ℝ, (9 / 4 - 4 * (Real.sin (A / 2) - 1 / 4) ^ 2) ≤ 9 / 4   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_14729; immutable original Prove2Me node 178b872c-a50b-4048-b7cb-c3e6c4061967

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