cos五分之π 乘以cos五分之二π
题目
cos五分之π 乘以cos五分之二π
答案
原式=2sin(π/5)cos(π/5)cos(2π/5)/[2sin(π/5)]=sin(2π/5)cos(2π/5)/[2sin(π/5)]=2sin(2π/5)cos(2π/5)/[4sin(π/5)]=sin(4π/5)/[4sin(π/5)]=sin(π-π/5)/[4sin(π/5)]=sin(π/5)/[4sin(π/5)]=1/4
举一反三
我想写一篇关于奥巴马的演讲的文章,写哪一篇好呢?为什么好
最新试题
热门考点