1. In addition to their applications for data fitting, the Chebyshev polynomials Tn(x) are useful for approximating func
Posted: Thu May 19, 2022 12:32 pm
1. In addition to their applications for data fitting, the Chebyshev polynomials Tn(x) are useful for approximating functions. This problem is concerned with approximations of the type f(x) – Sn(x), where Sn(x) knCnTn(x). (*) N n=0 if n = 0, Here {cn} is a set of constants that depend on f, and kn = -{ otherwise. (a) Let m and n be nonnegative integers. Use the substitution x = cos 8 to show that the Chebyshev polynomials Tn (2) satisfy the orthogonality relationship 1 if m= n, | Tm(z)Ty() dc = TJ-1 1 - 22 kin 0 otherwise. = COS Hint: 2 cos(m6) cos(no) (b) Consider the residual cos((m+n)e) + cos((m – n)o). т 2 RN [f(x) – Sn(x)]? d.x. V1 - x2 TJ-1 aRN Find an expression for ac; and hence deduce that the residual is minimised if Cj - L1,(dr, j = 0,1.... 2 TJ-x2 z)f(x ,