Equation 6.8.8D76FBA2B036A

\begin{equation} \int _{S^{2n-1}}|F(x+t\omega )|^2\, \mathrm dS(\omega )\geq t^{2k}\int _{S^{2n-1}}|P_ k|^2\, \mathrm dS, \qquad \int _{S^{2n-1}}|P_ k|^2\, \mathrm dS>0. \end{equation}