Given points \(P(x_1,\dots ,x_n)\) and \(Q(y_1,\dots ,y_n)\) in \(\RNrSpc{n}\), the length of the arrow \(\Arrow{P}{Q}\) from \(P\) to \(Q\) is

\[\Length{\Arrow{P}{Q} }\ \DefEq \ \Dstnc{P}{Q}\ =\ \sqrt{(y_1-x_1)^2+\cdots +(y_n-x_n)^2}.\]