The inverse function of that restricted sine function is called the arcsine function. 被限定的正弦函数之反函数叫做反正弦函数。
While for the sinusoidal approximation method, a detail derivation of the amplitude of each sinusoidal function is re-derived for completeness. 为完整性,文中亦详细推导正弦函数近似法中各个频率之振幅。