左边=(1-cos2α)/2+(1+cos(2α+π/3))/2+sinαcos(α+π/6)=1+1/2[cos(2α+π/3)-cos2α]+1/2[sin(2α+π/6)-1/2]=3/4-1/2cos2α+1/2[sin(2α+π/6)-sin(2α-π/6)]=3/4-1/2cos2α+1/2[2cos2αsinπ/6]=3/4=右边
