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Lean-Workbook Plus 41357: Trigonometric identity

Proved
WorkbookRestored.plus_41357

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

lean-workbookrestored-importssource-checked

For every real xx, tan⁡x=sin⁡x/cos⁡x\tan x=\sin x/\cos x, using Lean’s total tangent and division.

Source: Lean-Workbook row lean_workbook_plus_41357 (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_41357 (x : ℝ) : tan x = sin x / cos x   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_41357; immutable original Prove2Me node e289bf15-4e49-4f94-b432-09ef241ce803

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