摘要: \begin{align*}\sin^2 A+\sin^2B+\sin^2C &=\frac{1-\cos 2A}{2}+\frac{1-\cos 2B}{2}+\frac{1-\cos 2C}{2}\\ &=\frac{3}{2}-\frac{1}{2}(\cos 2A+\cos 2B+\cos 阅读全文
posted @ 2017-10-05 11:04 皇家大鹏鹏 阅读(372) 评论(0) 推荐(0)