楼上肆意刷分啊,答非所问1-cosx=2sin(x/2)利用二倍角公式2sin²(x/2)=2sin(x/2)sin²(x/2)-sin(x/2)=0sin(x/2)[sin(x/2)-1]=0sin(x/2)=0或sin(x/2)=1x/2=kπ或x/2=2kπ+π/2x=2kπ或x=4kπ+π,k∈Z...