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.
His workers channelled the water to allow it to power a series of corn mills along the Dee providing the city with a steady supply of flour and employing a large number of people.
法证明幂级数
可以逐项微分
叶系数
工人们将这些水引导起来，为
沿岸
磨坊提供动力，为该市提供了稳定
