By a translation of axes, points $\mathbf{S}\left(x_1, y_1\right)$ and $\mathbf{T}\left(x_2, y_2\right)$ are given new coordinates $\left(x_1^{\prime}, y_1^{\prime}\right)$ and $\left(x_2^{\prime}, y_2^{\prime}\right)$, respectively, in accordance with Equations (2) on page 171. Verify algebraically that
$$
\sqrt{\left(x_2^{\prime}-x_1^{\prime}\right)^2+\left(y_2^{\prime}-y_1^{\prime}\right)^2}=\sqrt{\left(x_2-x_1\right)^2+\left(y_2-y_1\right)^2}
$$
and interpret this fact geometrically.