摘要：拼错的： accident -> acciedent accuracy -> accuration admiration -> admirion arrangement -> arrangment anxiety -> anxioty care -> careness competitive -> 阅读全文

摘要：和差角公式 \(\sin(\alpha+\beta)=\sin\alpha \cos\beta+\cos\alpha \sin\beta\) \(\sin(\alpha-\beta)=\sin\alpha \cos\beta-\cos\alpha \sin\beta\) \(\cos(\alpha+ 阅读全文