  We report a measurement of the differential cross section, d{\sigma}/d(cos
{\theta}t), for top-quark-pair production as a function of the top-quark
production angle in proton-antiproton collisions at sqrt{s} = 1.96 TeV. This
measurement is performed using data collected with the CDF II detector at the
Tevatron, corresponding to an integrated luminosity of 9.4/fb. We employ the
Legendre polynomials to characterize the shape of the differential cross
section at the parton level. The observed Legendre coefficients are in good
agreement with the prediction of the next-to-leading-order standard-model
calculation, with the exception of an excess linear-term coefficient, a1 = 0.40
+- 0.12, compared to the standard-model prediction of a1 =
0.15^{+0.07}_{-0.03}.
