A relatively direct method is expounded in this paper to prove the termwise differentiation of power series, and a simple method is expressed to calculate the Fourier coefficient.
用比较直接的方法证明幂级
的和

收敛域内可以逐项微分的公式;并得到了计算傅立叶系
的一种简便方法.
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But equally important is that suppliers such as banks and tech firms (in developed markets) and telecoms companies (in emerging ones) are developing fast, easy-to-use payment technologies from which they can pull data and pocket fees.
但同样重要的
,银行和科技公司(在发达市场)以及电信公司(在新兴市场)等供应商正在开发快捷简便的支付技术,这种数据可以支持从中获取数据和收取小额费用。