English
Uncurrying the nested single injection recovers the canonical single injection corresponding to the pair (a,b).
Русский
Раскругив последовательную единичную инъекцию восстанавливает каноническую инъекцию, соответствующую паре (a,b).
LaTeX
$$$\Sigma.uncurry(\Pi.mulSingle a (\Pi.mulSingle b x)) = \Pi.mulSingle (\Sigma.mk a b) x$$$
Lean4
@[to_additive (attr := simp)]
theorem uncurry_mulSingle_mulSingle [DecidableEq α] [∀ a, DecidableEq (β a)] [∀ a b, One (γ a b)] (a : α) (b : β a)
(x : γ a b) : Sigma.uncurry (Pi.mulSingle a (Pi.mulSingle b x)) = Pi.mulSingle (Sigma.mk a b) x := by
rw [← curry_mulSingle ⟨a, b⟩, uncurry_curry]