English
If f1 and f2 are equal on s, then MonotoneOn f1 s is equivalent to MonotoneOn f2 s.
Русский
Если f1 и f2 совпадают на s, то MonotoneOn(f1,s) эквивалентно MonotoneOn(f2,s).
LaTeX
$$$\\forall {\\alpha}, {\\beta}, {\\gamma},\\ s: Set\\alpha,\\ f_1,f_2: \\alpha \\to \\beta,\\ [Preorder\\alpha][Preorder\\beta]\\n( h : s.EqOn f_1 f_2 s ) \\to \\operatorname{MonotoneOn} f_1 s \\iff \\operatorname{MonotoneOn} f_2 s$$$
Lean4
theorem congr_monotoneOn (h : s.EqOn f₁ f₂) : MonotoneOn f₁ s ↔ MonotoneOn f₂ s :=
⟨fun h₁ => h₁.congr h, fun h₂ => h₂.congr h.symm⟩