The total differential scattering cross sections for H-2, N-2, and Ar with C2H2 were measured on an in-plane crossed molecular beam apparatus at collision energies of 1051, 1056, and 929 K, respectively. Well resolved rainbow oscillations for N-2 and Ar, and diffraction oscillations for H-2, showed two interference effects. Effective spherical and anisotropic potentials were obtained from analysis using single channel and infinite-order-sudden (IOS) methods, based on the semiclassical Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. The damping of oscillations showed the importance of anisotropy in the pair potentials. Total differential scattering cross sections calculated using the IOS method were in excellent agreement with the experimental data.