Arccos
反余弦
🗣️ 情景例句
Hello, my name is Susan and I am calling to confirm my reservation.
喂，你好，我叫苏珊，我大电话确定我的预定。
She wishes to hear from her friend.
她希望收到朋友的来信。
A bottle of glue.
一瓶胶水。