已知 cos π/5 =(根号5 +1）/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10cos_数学解答

已知 cos π/5 =(根号5 +1）/4 求 sin π/5,sin -π/5 ,sin 4π/5 ,sin 3π/10
cos π/5,cos -π/5 ,cos 4π/5 ,cos 3π/10 如果有空顺便做下这个呗.

人气：163 ℃　时间：2020-05-05 18:33:41

解答

cosπ/5=sinπ/5=x/r=(根号5 +1）/4 则y=√4²-√5+1=2√5sinπ/5=cosπ/5=y/r=2√5/4=√5/2sin-π/5=cosπ/5=-y/r=-√5/2sin4π/5=cos4π/5=y/r=√5/2sin3π/5=cos3π/5=y/r=√5/2 注:是2分之根5cos-π/5=sinπ...