lean_workbook_plus_18071

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

Prove that $\tan x$ is increasing on $\Big]-\frac\pi2,\frac\pi2\Big[$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_18071 : ∀ x y : ℝ, x ∈ Set.Ioo (-π / 2) (π / 2) ∧ y ∈ Set.Ioo (-π / 2) (π / 2) ∧ x < y → tan x < tan y   :=  by sorry

Source