English
If x = (a,b) is minimal, then a is minimal in the first coordinate.
Русский
Если x = (a,b) минимален, то a минимален в первой координате.
LaTeX
$$$\\forall {\\alpha : Type*} {\\beta : Type*} [Preorder \\alpha] [Preorder \\beta] {x : \\Prod \\alpha \\beta}, IsMin x \\rightarrow IsMin x.1$$$
Lean4
theorem fst (hx : IsMin x) : IsMin x.1 := fun c hc => (hx <| show (c, x.2) ≤ x from (and_iff_left le_rfl).2 hc).1