三角函数正弦值,余弦值比较大小 cos15π/8与cos14/9πcos515`与cos530`sin(-54π/7)与sin(-63π/8)
问题描述：
三角函数正弦值,余弦值比较大小
cos15π/8与cos14/9π
cos515`与cos530`
sin(-54π/7)与sin(-63π/8)
答
cos15π/8=cos(2π-15π/8)=cos(π/8)cos14/9π=cos(2π-14π/9)=cos(4π/9)cosx在[0,π]是减函数,所以cos(π/8)>cos(4π/9)即cos15π/8>cos14/9πcos515°=cos155°cos530°=cos170°同理cos155°>cos170°sin(-54...