Prove2Me

Lean-Workbook Plus 68742: Trigonometric identity

Proved
WorkbookRestored.plus_68742

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

lean-workbookrestored-importssource-checked

For all real x,yx,y, cosh⁡(x+y)=cosh⁡xcosh⁡y+sinh⁡xsinh⁡y\cosh(x+y)=\cosh x\cosh y+\sinh x\sinh y.

Source: Lean-Workbook row lean_workbook_plus_68742 (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_68742 (x y : ℝ) : cosh (x + y) = cosh x * cosh y + sinh x * sinh y   :=  by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, row lean_workbook_plus_68742; immutable original Prove2Me node 8224c24c-c2bb-4163-8483-1979584fe83d

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