在很多物理和力学的问题中常出现最高阶导数项带有小参数的微分方程。
In many problems of mechanics and physics there frequently appears the differential equation with the derivative term of the highest-order containing small parameters.
通过在积分换元、微分方程求解、多（一）元复合函数求全微分、偏导数及高阶偏导数中的应用举例，论述了一阶微分的形式不变性在微积分学中的作用不应被忽略。
Based on the theory of differential geometry and geodesy, the second order differential equation and the first differential relationship are derived on the regional earth ellipsoid in this paper.
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