Prove2Me

Lean-Workbook Plus 60372: Trigonometric identity

Proved
WorkbookRestored.plus_60372

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

lean-workbookrestored-importssource-checked

2sin⁡xcos⁡y=sin⁡(x+y)+sin⁡(x−y)2\sin x\cos y=\sin (x+y)+\sin(x-y)

Source: Lean-Workbook row lean_workbook_plus_60372 (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_60372 : ∀ x y : ℝ, 2 * sin x * cos y = sin (x + y) + sin (x - y)   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_60372; immutable original Prove2Me node cd16c49c-67d3-4a78-a879-e752e3900f01

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