Let \(f\) be continuous. Show that it does not affect the finiteness of \(\operatorname{VAR}_{p}(f ;[0, t])\) and the numerical value of \(\operatorname{var}_{p}(f ;[0, t])\) if we restrict ourselves to partitions not containing the endpoints 0 and \(t\) of the interval. (In this case we have to define the mesh as mesh of \(\Pi \cup\{0, t\}\) ).