∀ {α : Type u_1} {β : Type u_2} [inst : Mul α] [inst_1 : Preorder α] [inst_2 : Preorder β] {f g : β → α} {s : Set β}
  [MulLeftMono α] [MulRightStrictMono α], StrictAntiOn f s → AntitoneOn g s → StrictAntiOn (fun x => f x * g x) s