sin(x+π/6)-4sinx
=sinxcos(π/6)+cosxsin(π/6)-4sinx
=sinxcos(π/6)+cosx/2-4sinx
=sinx[cos(π/6)-4]+cosx/2
=Ksin(x+θ)
K=根号([cos(π/6)-4]²+[1/2]²)
cosθ=[cos(π/6)-4]
sinθ=1/2
函数sin(x+π/6)-4sinx的最大值和最小值
显而易见 K 与 -K