Lean-Workbook Plus 65697: Trigonometric identity

Proved

WorkbookRestored.plus_65697

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

lean-workbookrestored-importssource-checked

$\sin(8\pi/17)=\cos(\pi/34)$ .

Source: Lean-Workbook row lean_workbook_plus_65697 (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_65697 : Real.sin (8 * Real.pi / 17) = Real.cos (Real.pi / 34)   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_65697; immutable original Prove2Me node 439c94c2-43db-482a-9ff0-464264b59151

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