wǒ / men / xiān / zhèng / míng / zhè / ge / héng / děng / shì / zài / bǎ / tā / yìng / yòng / dào / hòu / miàn / de / jì / suàn / zhōng

我们先证明这个恒等式，再把它应用到后面的计算中。

We will first prove this identity and then apply it to the calculations that follow.