求祥细解析.

1个回答

  • 2向量a-向量b=2√3cosx--2sinx

    =4(√3/2cosx-1/2sinx)

    =4sin(π/3-x)=--4sin(x-π/3)

    因为x属於[0,π],所以x-π/3属於[---π/3,2π/3]

    sin(x-π/3)属於[---√3/2,1],--4sin(x-π/3)属於[-4,2√3]

    所以|--4sin(x-π/3) |属於[0,4]

    因为m>| 2a -b |恒成立,所以m>| 2a -b |的最大值

    所以m>4