Secondly some basic theorem and deducibility of the theory of the calculus of variations are explained simply and the two things based on the problems of variations of the changeless boundary and the movable one are discussed .

然后对变分原理的一些基本定理、推论进行了简单的介绍，并对固定边界变分问题和 可动边界变分问题两种 情况进行了讨论；