lean_workbook_plus_19388

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

prove that $\sin(-x) = -\sin(x)$ and $\cos(-x) = \cos(x)$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_19388 : ∀ x : ℝ, sin (-x) = -sin x   :=  by sorry

Source