Approximation theory is a study of selection of an element from a prescribed class of functions which is in some sense 'closer' to the given function with desired degree of accuracy. The problem of linear approximation can be described in the following way: Let C be the set of functions defined in the a fixed space A. If a function f on A is given ,can we find a linear combination P = a1 1 + a2 2 +.............+ an n, i C which is closed to the function f