Marsden identity

The Marsden identity expands $(x-t{)}^{k-1}$ in a B-spline basis with knot-polynomial coefficients.

The Marsden dual functionals extract coefficients in a B-spline expansion. If ${\psi }_i$ is the knot polynomial in the Marsden identity, then on polynomials of degree at most $k-1$ one such functional isand the right-hand side is independent of $x$.