求y=sinx*sin(x+60)的最大值

y=sinx(sinxcos60+cosxsin60) =1/2(sinx)^2+√3/2*sinxcosx cos2x=1-2(sinx)^2,所以(sinx)^2=(1-cos2x)/2 sin2x=2sinxcosx,sinxcosx=1/2*sin2x 所以y=√3/4*sin2x-1/4*cos2x+1/4 =√[(√3/4)^2+(1/4)^2]*sin(2x-a)+1/4 =1/2*s