lean_workbook_plus_71970

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by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Write as $E=a\sin u + b\sin (u+v) =(a+b\cos v)\sin u + (b\sin v)\cos u$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_71970 (a b : ℝ) (u v : ℝ) : a * sin u + b * sin (u + v) = (a + b * cos v) * sin u + (b * sin v) * cos u   :=  by sorry

Source