For (7.6.8) differentiate: use (7.2.1) for the
left-hand side, and (10.47.7) and the second of
(10.29.1) for the right-hand side.
The same method can be used for (7.6.10) and
(7.6.11).
For (7.6.9) write the coefficients in the Chebyshev-series
expansion of as integrals
(§3.11(ii)), then apply (5.12.5),
(7.6.2), and (13.6.9).