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lemma proved term proof

cosh_eq_one_iff

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formal statement (Lean)

 102private lemma cosh_eq_one_iff (t : ℝ) : cosh t = 1 ↔ t = 0 := by

proof body

Term-mode proof.

 103  constructor
 104  · intro h
 105    by_contra hne
 106    exact absurd h (ne_of_gt ((one_lt_cosh).mpr hne))
 107  · intro h; rw [h, cosh_zero]
 108
 109/-- J̃(lam, δ) = 0 iff δ is an integer, for lam ≠ 0. -/

used by (3)

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depends on (6)

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