The hole-doped cuprate high-temperature superconductors enter the pseudogap regime as their superconducting critical temperature, T-c, falls with decreasing hole density. Recent x-ray scattering experiments in YBa2Cu3O6+x observe incommensurate charge-density wave fluctuations whose strength rises gradually over a wide temperature range above T-c, but then decreases as the temperature is lowered below T-c. We propose a theory in which the superconducting and charge-density wave orders exhibit angular fluctuations in a six-dimensional space. The theory provides a natural quantitative fit to the x-ray data and can be a basis for understanding other characteristics of the pseudogap.