根據(jù)誘導(dǎo)公式可得cos(5/6π+x)= cos[π-(π/6—x)]
=- cos(π/6—x)=- 根號(hào)3/3,
sin平方的(x+π/3)=[1-cos(2x+2π/3)]/2
=[1+cos(π/3-2x)]/2……（根據(jù)誘導(dǎo)公式可知cos(2x+2π/3)= -cos(π/3-2x)）
cos(π/3-2x)= cos[2(π/6—x)]=2 cos² (π/6—x)-1=-1/3.
∴sin平方的(x+π/6)= [1+cos(π/3-2x)]/2=1/3.
∴cos(5/6π+x)—sin平方的(x+π/3)= - √3/3-1/3=-(√3+1)/3.