Define the distance between two vector u and v as
d(u,v) = ||u-v||. Show that d(u,w) <= d(u,v) + d(v,w)
Thanks for your help,
Are you allowed to use the fact that [tex]||a+ b||\le ||a||+ ||b||[tex]? If so this is very easy. If not, I recommend that you prove that statement first so you can use it!