问题描述: (cosπ/8+sinπ/8)(cos^3π/8-sin^3π/8) 1个回答 分类:数学 2014-10-14 问题解答: 我来补答 是要化简吗?(cosπ/8+sinπ/8)(cos³3π/8-sin³3π/8)=(cosπ/8+sinπ/8)(cosπ/8-sinπ/8)(cos²3π/8+cos3π/8sin3π/8+sin²3π/8)=(cos²π/8-sin²π/8)(1+1/2sin3π/4)=cosπ/4 × (1+1/2sin3π/4)(老实说我觉得你应该知道cosπ/4和sin3π/4的值了……)=cosπ/4 × (1+1/2sinπ/4)=√2/2 × (1+√2/4)=(2√2+1)/4 展开全文阅读