theorem
proved
term proof
Jlog_strictMonoOn_Ici0
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formal statement (Lean)
50theorem Jlog_strictMonoOn_Ici0 : StrictMonoOn Jlog (Set.Ici (0 : ℝ)) := by
proof body
Term-mode proof.
51 intro x hx y hy hxy
52 -- strict monotonicity inherits from `cosh` on `Ici 0`
53 have hcosh : Real.cosh x < Real.cosh y :=
54 Real.cosh_strictMonoOn hx hy hxy
55 -- subtracting 1 preserves strict inequality
56 -- rewrite the goal using `Jlog = cosh - 1`
57 rw [Jlog_eq_cosh_sub_one, Jlog_eq_cosh_sub_one]
58 exact sub_lt_sub_right hcosh 1
59
60end Cost
61end IndisputableMonolith