mathematics A real-valued function modelling the length of a
fulfil the following condition: the shortest way to reach a
point is to go straight toward it. Every
convex symmetric
closed surface surrounding point 0 introduces a norm by
surface have the same norm then.
calculated by summing up squares of all coordinates and taking
the square root; this is the essence of
Pythagorus'stheorem. In the infinite-dimensional case, the sum is
infinite or is replaced with an integral when the number of
(1998-07-05)