Definition
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[111] Let \(B_ 1, B_ 2\) be two normed vector spaces. A function \(f: B_ 1 β B_ 2\) is a linear isometry if it is linear and if
\begin{equation} \left\| z \right\| _{B_ 1} = \left\| f (z) \right\| _{B_ 2} β \ z β B_ 1~ ~ .\label{eq:isometria_ lineare} \end{equation}
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