The possibility to symmetry assign x-ray absorption spectra using x-ray emission spectroscopy is demonstrated. The oxygen K spectra of CO2 are used to illustrate the possibility to assign core excitations through excitation-energy and angular dependence of resonantly excited x-ray emission spectra. The Rydberg-associated structures just below the ionization threshold in the O K x-ray absorption spectrum are assigned to be mainly due to excitations to orbitals of sigma(g) character. The results, which contradict some previous literature assignments, are supported by quantum-chemical calculations.