sinπ/12-sin5π/12+2sinπ/8sin3π/8

来源：学生作业帮助网编辑：作业帮时间：2024/05/05 04:36:10

sinπ/12-sin5π/12+2sinπ/8sin3π/8
sinπ/12-sin5π/12+2sinπ/8sin3π/8

sinπ/12-sin5π/12+2sinπ/8sin3π/8
化成sin(15度)-sin(75度)+2sin(22.5度)sin(67.5度)
答案为0
步骤如下：
sin(15度)=sin(45度-30度)=(√6-√2)/4
sin(75度)=sin(45度+20度)=(√6+√2)/4
因为sin(22.5度)=sin(90度-67.5度)=cos(67.5度)
所以2sin(22.5度)sin(67.5度)=2sin(67.5度)cos(67.5度)=sin(135度)=√2／2
所以答案为0
很抱歉我没写步骤,谢谢你的提醒.

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