Prove2Me

Lean-Workbook Plus 25157: Trigonometric identity

Proved
WorkbookRestored.plus_25157

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

lean-workbookrestored-importssource-checked

For every real xx, sin⁡x=cos⁡(π/2−x)\sin x=\cos(\pi/2-x).

Source: Lean-Workbook row lean_workbook_plus_25157 (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_25157 (x : ℝ) : sin x = cos (π / 2 - x)   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_25157; immutable original Prove2Me node c8788d1a-9d31-49bb-992c-7a2f351a0b4a

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