  We revisit the ladder operators for orthogonal polynomials and re-interpret
two supplementary conditions as compatibility conditions of two linear
over-determined systems; one involves the variation of the polynomials with
respect to the variable z (spectral parameter) and the other a recurrence
relation in n (the lattice variable). For the Jacobi weight w(x) =
(1-x)^a(1+x)^b, x in [-1,1],we show how to use the compatibility conditions to
explicitly determine the recurrence coefficients of the monic Jacobi
polynomials.
