Arccos
反余弦
🗣️ 情景例句
Live and let live.
各人有各人的活法。
Is it long drive from here to the dapartment store?
从这里到百货公司开车也要走很多时间。
Speculations about is nature have been going on for literally thousands of years,
人们对睡眠作用的种种猜测，确实有数千年之久。