Arccosine
反余弦
🗣️ 情景例句
I don't know how to thank you enought.
我不知道应该如何感谢你。
What shall I send him for his the New Year?
我要送他什么东西作为新年礼物？
I must always keep on trying to do my best.
我必须始终继续作出最大的努力。