cos (180/5)* cos(360/5)=?
收藏:
0
点赞数:
0
评论数:
0
3个回答

cos (180/5)* cos(360/5)

=cos 36* cos72

=cos 36*sin 36*cos72/sin 36

=1/2sin72*cos72/sin 36

=1/4sin144/sin 36

=1/4sin36/sin 36

=1/4

点赞数:
0
评论数:
0
关注公众号
一起学习,一起涨知识