The implicit function theorem is. along with its close cousinthe inverse func- tion theorem， one of the most important， and oneof the oldest， paradigms in modcrn mathemarics. One can see thegerm of the idea for the implicir func tion theorem in the writingsof Isaac Newton （1642-1727）， and Gottfried Leib-niz's （1646-1716）work cxplicitty contains an instance of implicitdifferentiation.
　　Whilc Joseph Louis Lagrange （1736-1813） found a theorcm that isessentially a version of the inverse function theorem， ic wasAugustin-Louis Cauchy （1789-1857） who approached the implicitfunction theorem with mathematical rigor and it is he who isgencrally acknowledgcd as the discovcrer of the theorem. InChap-ter 2， we will give details of the contributions of Newton，Lagrange， and Cauchy to the development of the implicit functiontheorem.