theorem
proved
term proof
cosh_eq_one_iff
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formal statement (Lean)
34private theorem cosh_eq_one_iff (t : ℝ) : Real.cosh t = 1 ↔ t = 0 := by
proof body
Term-mode proof.
35 constructor
36 · intro h
37 by_contra hne
38 have hgt : 1 < Real.cosh t := Real.one_lt_cosh.mpr hne
39 linarith
40 · intro h
41 simp [h]
42
43/-- The abstract zero-location composition law needed by Vector C. -/