Moreprecisely，by（i），Imeanasystematicpresentationofthematerialgovernedbythedesireformathematicalperfectionandcompletenessoftheresults.Incontrastto（i），approach（ii）startsoutfromthequestion"Whatarethemostimportantapplications？"andthentriestoanswerthisquestionasquicklyaspossible.Here，onewalksdirectlyonthemainroadanddoesnotwanderintoalltheniceandinterestingsideroads.　　Thepresentbookisbasedonthesecondapproach.Itisaddressedtoundergraduateandbeginninggraduatestudentsofmathematics，physics，andengineeringwhowanttolearnhowfunctionalanalysiselegantlysolvesma~hematicalproblemsthatarerelatedtoourrealworldazldthathaveplayedanimportantroleinthehistoryofmathematics.Thereadershouldsensethatthetheoryisbeingdeveloped，notsimplyforitsownsake，butfortheeffectivesolutionofconcreteproblems.