Let us say that the principle of localization holds at the class of functions F at point x0 ∈ [0, π] for the Lagrange –Sturm – Liouville interpolation process LSLn (f, x) if limn→∞ LSLn (f, x0) − LSLn (g, x0) = 0 follows from the fact that the condition f(x) = g<