解:设y=3cosx-sinx
y=2[3^((1/2)/2cosx-(1/2)sinx]
=2(sin60cosx-cos60sinx)
=2sin(60-x)
即,根号3cosx-sinx=2sin(60-x)
当,x=0时,原式=2sin60=2*根号3/2=根号3