English
image₂ f s (insert b t) = (s.image (λ a. f a b)) ∪ image₂ f s t.
Русский
image₂ f s (insert b t) = (s.image (λ a. f a b)) ∪ image₂ f s t.
LaTeX
$$$\\operatorname{image}_2 f s (\\operatorname{insert} b\\, t) = (s.\\operatorname{image} (\\lambda a. f a b)) \\cup \\operatorname{image}_2 f s t$$$
Lean4
theorem image₂_inter_left [DecidableEq α] (hf : Injective2 f) : image₂ f (s ∩ s') t = image₂ f s t ∩ image₂ f s' t :=
coe_injective <| by
push_cast
exact image2_inter_left hf