Illustration: Length of an Arrow

The length of the arrow joining \(P(x_1,\dots ,x_n)\) to \(Q(y_1,\dots ,y_n)\) is given by the formula

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

This means that the length of an arrow is defined to be the distance between its end points.