Metric Space - Product Metric Spaces

Product Metric Spaces

If are metric spaces, and N is the Euclidean norm on Rn, then is a metric space, where the product metric is defined by

and the induced topology agrees with the product topology. By the equivalence of norms in finite dimensions, an equivalent metric is obtained if N is the taxicab norm, a p-norm, the max norm, or any other norm which is non-decreasing as the coordinates of a positive n-tuple increase (yielding the triangle inequality).

Similarly, a countable product of metric spaces can be obtained using the following metric

An uncountable product of metric spaces need not be metrizable. For example, is not first-countable and thus isn't metrizable.

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