English
The maximum of a and b equals b if a < b, otherwise it equals a (i.e., max a b = if a < b then b else a).
Русский
Максимум(a,b) равен b, если a < b, иначе равен a.
LaTeX
$$$ \\max a b = \\begin{cases} b, & a < b \\\\ a, & \\text{иначе} \\end{cases} $$$
Lean4
theorem max_def_lt (a b : α) : max a b = if a < b then b else a := by rw [max_comm, max_def, ← ite_not];
simp only [not_le]