Arccos
反余弦
🗣️ 情景例句
How ofter have met with our competitors?
你多久遭遇我们的竞争对手一次？
Give my best to your family.
代我向你们全家问好。
Do you remember when the three of us went on a picnic?
我们三个人一起搞过野餐，你还记得吗？