Prove2Me

Lean-Workbook Plus 60336: Trigonometric identity

Proved
WorkbookRestored.plus_60336

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

lean-workbookrestored-importssource-checked

cos⁡36∘−cos⁡72∘=sin⁡54∘−sin⁡18∘\cos 36^\circ-\cos 72^\circ=\sin 54^\circ-\sin 18^\circ

Source: Lean-Workbook row lean_workbook_plus_60336 (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_60336 : Real.cos (36 * Real.pi / 180) - Real.cos (72 * Real.pi / 180) = Real.sin (54 * Real.pi / 180) - Real.sin (18 * Real.pi / 180)   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_60336; immutable original Prove2Me node a5050888-6cac-4b7c-921a-6347d8a2e160

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