These sum problems are all difficult for using elementary method and analysis method, but we can easily solve these sum problems by using the probability method.

而这几个公式的求和问题不论是用初等方法或分析方法都是比较困难的，但用概率的方法却比较容易解决。

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The transformation of Gaussian beams is taken as an example, an approximate analytical propagation expression in terms of a sum of elementary functions is derived.

以高斯光束的变换为例，推导出了一个表示为初等函数之和的近似解析传输公式。

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To an object, the distribution of the object wave on the recording plane is the sum of all the distributions of the elementary circular-viewing hologram.

实际物体在记录面上的物光分布可以看成是物体上所有物点的基元周视全息物光分布的叠加。

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