例如，在微积分课程中，记下分步积分法的公式并不是特别难。

For example, in a calculus course it's not terribly difficult to memorize the formula for integration by parts for integrals.

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利用广义拉盖尔多项式的级数表达式和分步积分法，给出了各向同性谐振子径向矩阵元的另一种表达式。

Another expression of the radial matrix elements for isotropic harmonic oscillator is obtained by using progressional expression of the generalized Laguerre polynomial and the partial integration.

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