f(x)=[(asin2x)/2]+[b(cos2x+1)]/2
=[(asin2x+bcos2x)/2]+(b/2)
f(0)=b=3
f(pi/6)=[(a根号3)/4]+(b/4)+(b/2)=3/2
解得a=-(根号3)
所以f(x)=-{[(根号3)sin2x-3cos2x]/2}+(3/2)
=-(根号3)sin[2x-(pi/3)]+(3/2)
所以
当2x-(pi/3)=(pi/2)+2kpi时,f(x)取最小值
即x=(5pi/12)+kpi
f(x)min=-(根号3)+(3/2)
当2x-(pi/3)=-(pi/2)+2kpi时,f(x)取最大值
即x=(-pi/12)+kpi
f(x)max=(根号3)+(3/2)