Further generalizations of the parallelogram law

In recent work by Alessandro Fonda, a generalization of the parallelogram law in any dimension $N\ge 2$ was given by considering the ratio of the quadratic mean of the measures of the $N-1$-dimensional diagonals to the quadratic mean of the measures of the faces of a parallelotope. In this paper, we provide a further generalization considering not only $(N-1)$-dimensional diagonals and faces, but the $k$-dimensional ones for every $1\le k\le N-1$.