If X and Y are two metric spaces, then a function f : X → Y is an isometry means that it is a bijection that preserves distances: d(p,q) = d(f(p), f(q)).
(a) Let X = ℑ² be the plane with the taxicab norm ||⃗v||₁ and corresponding metric d₁(⃗v, ⃗w), and let Y = ℑ² be the plane with the sup norm ||⃗v||∞ and the corresponding metric d∞(⃗v, ⃗w). Prove that there is an isometry between X and Y. (Hint: There is one that is a linear transformation.)
(b) Let X = ℑ² be the plane with the taxicab norm ||⃗v||₁ and corresponding metric d₁(⃗v, ⃗w), and let Y = ℑ² be the plane with the Euclidean norm ||⃗v||₂ and the corresponding metric d₂(⃗v, ⃗w). Prove that there isn't isometry between X and Y. (Hint: Isometric paths are always unique in one of X and Y, but not in the other one.)
*(c) Prove that there is no linear isometry between ℑ³ with the taxicab norm ||⃗v||₁ and ℑ³ with the sup norm ||⃗v||∞