Definition
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[0TK] Given \((M_ 1,d_ 1)\) and \((M_ 2,d_ 2)\) metric spaces, a map \(π:M_ 1β M_ 2\) is called an isometry if
\begin{equation} β x,yβ M_ 1, ~ ~ d_ 1(x,y)=d_ 2(π(x),π(y))~ ~ .\label{eq:isometria} \end{equation}
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