Introduction

In this lecture, integral formulations of a boundary value problem are developed. There are two types of integral formulations :

• Weak or Weighted residual formulation and s
• Variational formulation

In finite element method, the solution of a boundary value problem is obtained by using one of these two integral formulations. When it is difficult to solve the differential equation of a boundary value problem, this method provides an alternative way to obtain the solution. But, usually, it is an approximate solution.