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