1、化简函数f(x)=(sin^4 x+cos^4 x+sin^2 xcos^2 x)/(2-sin2x)

1个回答

  • 1、f(x)=(sin^4 x+cos^4 x+sin^2 xcos^2 x)/(2-sin2x)

    =[(sin^2 x+cos^2 x)^2-2sin^2 xcos^2 x+sin^2 xcos^2 x]/(2-sin2x)

    =(1-sin^2 xcos^2 x)/(2-sin2x)

    =[(1-sinxcosx)(1+sinxcosx)]/[2(1-sinxcosx)]=(1+sinxcosx)/2

    2、f(x)=4sinxsin^2(π/4 +x/2)+cos2x

    =2sinx(cosx/2+sinx/2)^2+cos2x

    =2sinx(1+sinx)+cos2x

    =2sinx+2sin^2 x+1-2sin^2 x

    =2sinx+1

    (1)y=f(ωx)=2sinωx+1

    要使y=f(ωx)在区间[-π/2,2π/3]上是增函数

    则T≥4*(2π/3)=8π/3

    T=2π/ω 解得:ω≤3/4

    (2)f(x)的T为2π,A是B的子集

    根据题意得,f(x)在π/6≤x≤2π/3之间的取值范围为[-1,3]

    则 f(x)-m1

    3、(1)f(x)=2cos^2 x+ 根号3 sin2x+α

    =cos2x+1+ 根号3 sin2x+α

    =2sin(x+π/6)+α+1 T=2π

    则在[-π/6,π/6]上最大值与最小值之和分别在π/6和-π/6处取得

    即2sin(π/6+π/6)+α+1+2sin(-π/6+π/6)+α+1=3

    解得:α=(1-根号3)/2

    (2)要使f(x)=0在[0,π]内有两相异实根x1 x2

    则0