One Example in Monotone Approximation

For each non-negative integerna functionf=fnis constructed such thatfhas a continuous and non-negative derivativef? onI:=?1, 1] andformula]whereEn(f?) (E(1)n+1(f)) is the value of the best uniform approximation onIof the functionf? (f) by arbitrary (monotone onI) algebraic polynomials of degree ?n(n+1).