The approximation of functions by algebraic polynomials, trigonometric polynomials and splines, is not only an important topic of mathematical studies but also provides powerful mathematical tools to represent non-arithmetic quantities by arithmetic quantities to achieve the accuracy to a desired degree. The role of linear positive operators is very important in the approximation theory. The theorem given by Weierstrass is the basis of theory of approximation for the functions of real variable and has huge importance in the whole of mathematical analysis.The main purpose of this book is to...