English
A simplified equivalence: IsClosedMap( Sum.elim f g ) iff IsClosedMap f ∧ IsClosedMap g.
Русский
Упрощённая эквивалентность: IsClosedMap( Sum.elim f g ) эквивалентно IsClosedMap f ∧ IsClosedMap g.
LaTeX
$$$$\\mathrm{IsClosedMap}(\\mathrm{Sum.elim} f g) \\iff \\mathrm{IsClosedMap} f \\land \\mathrm{IsClosedMap} g.$$$$
Lean4
@[simp]
theorem isClosedMap_sumElim {f : X → Z} {g : Y → Z} : IsClosedMap (Sum.elim f g) ↔ IsClosedMap f ∧ IsClosedMap g := by
simp only [isClosedMap_sum, Sum.elim_inl, Sum.elim_inr]