根号3 /2 ×sin2x+1/2cos2x=3/5(√3/2)sin2x=3/5-(1/2)cos2x两边平方(3/4)(1-cos²2x)=9/25-(3/5)cos2x+(1/4)cos²2xcos²2x-(3/5)cos2x-39/100=0解得cos2x=(3±4√3)/10