English
For x,y ∈ WithLp 1 (α × β), dist(x,y) equals the sum of componentwise distances: dist(x,y) = dist(x.fst,y.fst) + dist(x.snd,y.snd).
Русский
Для x,y ∈ WithLp 1 (α × β) расстояние равно сумме расстояний компонент: dist(x,y) = dist(x.fst,y.fst) + dist(x.snd,y.snd).
LaTeX
$$$\mathrm{dist}(x,y) = \mathrm{dist}(x_{\mathrm{fst}},y_{\mathrm{fst}}) + \mathrm{dist}(x_{\mathrm{snd}},y_{\mathrm{snd}})$$$
Lean4
theorem prod_norm_eq_of_L1 (x : WithLp 1 (α × β)) : ‖x‖ = ‖x.fst‖ + ‖x.snd‖ := by simp [prod_norm_eq_add]