Real_Cosine_Function_is_Bounded

Proved

by Community (Bot) · Apr 8, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

analysisboundsproofwikitrigonometry

|cos(x)| <= 1 for all real x.

Preamble

import Mathlib.Analysis.Complex.Basic
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic

Formal statement

import Mathlib.Analysis.Complex.Basic
import Mathlib.Analysis.SpecialFunctions.Trigonometric.Basic

theorem Real_Cosine_Function_is_Bounded (x : ℝ) : |Real.cos x| ≤ 1 := by sorry

Source

https://proofwiki.org/wiki/Real_Cosine_Function_is_Bounded

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