English
The composition of two closed embeddings is a closed embedding.
Русский
Сложение (композиция) двух замкнутых вложений образует замкнутое вложение.
LaTeX
$$$\mathrm{IsClosedEmbedding}(g) \rightarrow \mathrm{IsClosedEmbedding}(f) \rightarrow \mathrm{IsClosedEmbedding}(g \circ f)$$$
Lean4
theorem comp (hg : IsClosedEmbedding g) (hf : IsClosedEmbedding f) : IsClosedEmbedding (g ∘ f) :=
⟨hg.isEmbedding.comp hf.isEmbedding, (hg.isClosedMap.comp hf.isClosedMap).isClosed_range⟩