English
image₂ f (insert a s) t = (t.image (\\lambda b. f a b)) ∪ image₂ f s t.
Русский
image₂ f (insert a s) t = (t.image (λ b. f a b)) ∪ image₂ f s t.
LaTeX
$$$\\operatorname{image}_2 f (\\operatorname{insert} a\\, s)\\, t = (t.\\operatorname{image} (\\\\lambda b. f a b)) \\cup \\operatorname{image}_2 f s t$$$
Lean4
@[simp]
theorem image₂_insert_right [DecidableEq β] : image₂ f s (insert b t) = (s.image fun a => f a b) ∪ image₂ f s t :=
coe_injective <| by
push_cast
exact image2_insert_right