√3tan12-3 =√3sin12°/cos12-3 =(√3sin12°-3cos12°)/cos12 =2√3sin(12°-60°)/cos12 =-2√3sin48°/cos12° =-4√3sin24°cos24°/cos12° =-8√3sin12°cos12°cos24°/cos12° =-8√3sin12°cos24° sin12°(4(cos12°)^2-2) =sin12°(4(cos24°+1)/2-2) =sin12°*2cos24° =2sin12°cos24° 所以（√3tan12°-3）/[sin12(4(cos12°)^2-2)]=-4√3