Coupled with its sequel, this book gives a connected, unified exposition
of Approximation Theory for functions of one real variable. It describes
spaces of functions such as Sobolev, Lipschitz, Besov
rearrangement-invariant function spaces and interpolation of operators.
Other topics include Weierstrauss and best approximation theorems,
properties of polynomials and splines. It contains history and proofs
with an emphasis on principal results.