若函数f(x)的解析式为f(x)=2tanx-(2sin^2 (x/2) -1)/(sinx/2*c

若函数f(x)的解析式为f(x)=2tanx-(2sin^2 (x/2) -1)/(sinx/2*c

1）f(x)=2tanx-(2sin^2 (x/2) -1)/(sinx/2*cosx/2) f(x)=2tanx +cos x /(1/2 * sin x ) =2tanx +2 cotx =2[(sin x /cos x )+(cos x /sin x)]=4/sin(2x) 将π/12带入,=8 1）求sin^2+sin2α/cos^2 α +cos2α sinα=4/5 ,cosα=3/5,(sinα)^2=16/25,(cosα)^2=9/25 cos2α=2(cosα)^2-1=-7/25 sinα=2sinαcosα=24/25 (sin^2+sin2α)/(cos^2 α +cos2α) =(16/25+24/25)/(9/25-7/25)=40/2=20 2）tan(α-5π/4) tan(α-5π/4) =(tanα -tan5π/4)/(1+tanα*tan5π/4),tan5π/4=1,sinα=4/5 ,cosα=3/5,tanα=4/3,带入tan(α-5π/4)中 =(tanα -tan5π/4)/(1+tanα*tan5π/4) =(4/3-1)/(1+4/3) =1/7======以下答案可供参考======供参考答案1:1）f(x)=2tanx-(2sin^2 (x/2) -1)/(sinx/2*cosx/2) f(x)=2tanx +cos x /(1/2 * sin x )=2tanx +2 cotx =2[(sin x /cos x )+(cos x /sin x)]=4/sin(2x)将π/12带入,=8 2）已知α为锐角,1）求sin^2+sin2α/cos^2 α +cos2αsinα=4/5 ,cosα=3/5,(sinα)^2=16/25,(cosα)^2=9/25cos2α=2(cosα)^2-1=-7/25sinα=2sinαcosα=24/25(sin^2+sin2α)/(cos^2 α +cos2α)=(16/25+24/25)/(9/25-7/25)=40/2=202）tan(α-5π/4) tan(α-5π/4)=(tanα -tan5π/4)/(1+tanα*tan5π/4),tan5π/4=1,sinα=4/5 ,cosα=3/5,tanα=4/3,带入tan(α-5π/4)中=(tanα -tan5π/4)/(1+tanα*tan5π/4)=(4/3-1)/(1+4/3)=1/7供参考答案2:1。若函数f(x)的解析式为f(x)=2tanx-(2sin^2 (x/2) -1)/(sinx/2*cosx/2) 则f(π/12)是f(x)=2tg x +cos x /(1/2 * sin x )=2tg x +2 ctg x =2[(sin x /cos x )+(cos x /sin x)]=2/[(1/2)sin 2x]将π/12带入,可算的答案为82。已知α为锐角,且sinα=4/5 （1）求sin^2+sin2α/cos^2 α +cos2α的值 题目不完整,没法给你算（2）tan(α-5π/4) ,tan(α-5π/4)=(tanα -tan5π/4)/(1+tanα*tan5π/4),因为tan5π/4=tanπ/4=1,又因为sinα=4/5 ,所以cosα=3/5,所以tanα=4/3,带入tan(α-5π/4)=(tanα -tan5π/4)/(1+tanα*tan5π/4)=(4/3-1)/(1+4/3)=1/7

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