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  • 函數(shù)f(x)=(1+1/tanx)sin^2x-2sin(x+π/4)sin(x-π/4).若tana=2,求f(a).若x屬于[π/12,π/2],求取值范圍

    函數(shù)f(x)=(1+1/tanx)sin^2x-2sin(x+π/4)sin(x-π/4).若tana=2,求f(a).若x屬于[π/12,π/2],求取值范圍
    函數(shù)f(x)=(1+1/tanx)sin^2x-2sin(x+π/4)sin(x-π/4).若tana=2,求f(a).若x屬于[π/12,π/2]求f(x)取值范圍
    數(shù)學(xué)人氣:469 ℃時(shí)間:2019-09-29 00:56:07
    優(yōu)質(zhì)解答
    f(x)=sin^2x+sinxcosx-sin^2x+cos^2x
    =sinxcosx+cos^2x
    =sin2x/2+(1+cos2x)/2
    =sin2x/2+cos2x/2+1/2
    (1)f(a)=sin2a/2+cos2a/2+1/2
    根據(jù)萬(wàn)能公式得 sin2a=tana/(1+tan^2a)=2/5 cos2a=(1-tan^2a)/(1+tan^2a)=-3/5
    f(a)=1/5-3/10+1/2=2/5
    (2)f(x)=sin2x/2+cos2x/2+1/2=√2sin(2x+π/4)/2+1/2
    π/12f(x)=(1+1/tanx)sin^2x-2sin(x+π/4)sin(x-π/4).怎么變這個(gè)f(x)=sin^2x+sinxcosx-sin^2x+cos^2x
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