English
For complete lattice α, f: ι → α, iSup of partialSups f i equals iSup of f i, i.e., partialSups f i = ⨆ j ≤ i, f j.
Русский
Для полной решётки α, ⨆ i (partialSups f i) = ⨆ i f i – эквивалентно: partialSups f i = ⨆ { j ≤ i } f j.
LaTeX
$$$\operatorname{partialSups} f\, i = \bigvee_{j \le i} f(j)$$$
Lean4
theorem partialSups_eq_biSup (f : ι → α) (i : ι) : partialSups f i = ⨆ j ≤ i, f j := by
simpa only [iSup_subtype] using partialSups_eq_ciSup_Iic f i