(1)3根号15sinx 3根号5cosx的周期,单调区间,最大值最小值

2个回答

  • ,请看如下解答

    (1)

    (3√15sinx)(3√5)cosx

    =15√3sinxcosx

    =(15√3/2) sin2x

    周期T=2π/2=π

    单调增区间:[-π/4+kπ/2,π/4+kπ/2]

    单调减区间:[π/4+kπ/2,3π/4+kπ/2] k∈Z

    最大值15√3/2

    最小值-15√3/2

    (2)

    3/2 cosx-√3/2 sinx

    =√3 (√3/2 cosx- 1/2 sinx)

    =√3(sinπ/3cosx-cosπ/3sinx)

    =√3sin(π/3-x)

    =-√3sin(x-π/3)

    周期T=2π

    由π/2+2kπ≤x-π/3≤3π/2+2kπ

    得5π/6+2kπ≤x≤11π/6+2kπ

    递增区间:[5π/6+2kπ,11π/6+2kπ] k∈Z

    最大值√3

    最小值-√3