English
The image of D ∪ E under inclusion equals the union of images: image(val)(D ∪ E) = image(val)(D) ∪ image(val)(E).
Русский
Образ D ∪ E под инклюзией равен объединению образов: image(val)(D ∪ E) = image(val)(D) ∪ image(val)(E).
LaTeX
$$$\\operatorname{image}(\\operatorname{val})(D \\cup E) = \\operatorname{image}(\\operatorname{val}) D \\cup \\operatorname{image}(\\operatorname{val}) E$$$
Lean4
@[simp]
theorem image_val_union : (↑(D ∪ E) : Set α) = ↑D ∪ ↑E :=
image_union _ _ _