English
Let f be a function on pairs; then image2 f (s ∪ s') (t ∩ t') is contained in image2 f s t ∪ image2 f s' t'.
Русский
Пусть f определяется на парах; тогда image2 f (s ∪ s') (t ∩ t') ⊆ image2 f s t ∪ image2 f s' t'.
LaTeX
$$$\\operatorname{image}_2 f (s \\cup s') (t \\cap t') \\subseteq \\operatorname{image}_2 f s t \\cup \\operatorname{image}_2 f s' t'$$$
Lean4
theorem image2_inter_union_subset_union : image2 f (s ∩ s') (t ∪ t') ⊆ image2 f s t ∪ image2 f s' t' :=
by
rw [image2_union_right]
exact union_subset_union (image2_subset_right inter_subset_left) (image2_subset_right inter_subset_right)