fx=m.n=sinx√3Acosx+ (A/2)co2x=
f(x)= A[√3/2sin2x+(1/2)cos2x]
∵f(x)max=6.
∴f(x)max=Asin(2x+π/6)=6.即sin(2x+π/6)=1.
∴A=6.