Lean-Workbook Plus 33234: Trigonometric identity

Proved

WorkbookRestored.plus_33234

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

lean-workbookrestored-importssource-checked

If $\sin(x+\pi/4)=0$ , then $x=k\pi-\pi/4$ for some integer $k$ .

Source: Lean-Workbook row lean_workbook_plus_33234 (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_33234  (x : ℝ)
  (h₀ : Real.sin (x + Real.pi / 4) = 0) :
  ∃ k : ℤ, x = k * Real.pi - Real.pi / 4   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_33234; immutable original Prove2Me node 65d1ad15-c7c2-4efb-8321-c10482ce89f9

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