6道高一数学填空选择!求帮忙!在线等!1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?A. 3 B. 21/10 C.1/3 D.1/302.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?A.24/25 B.-24/25 C.4/5 D.7/253.函数y=(sinx)
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![6道高一数学填空选择!求帮忙!在线等!1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?A. 3 B. 21/10 C.1/3 D.1/302.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?A.24/25 B.-24/25 C.4/5 D.7/253.函数y=(sinx)](/uploads/image/z/3936040-16-0.jpg?t=6%E9%81%93%E9%AB%98%E4%B8%80%E6%95%B0%E5%AD%A6%E5%A1%AB%E7%A9%BA%E9%80%89%E6%8B%A9%21%E6%B1%82%E5%B8%AE%E5%BF%99%21%E5%9C%A8%E7%BA%BF%E7%AD%89%211.%E5%B7%B2%E7%9F%A5tan%CE%B1%3D3+%E5%88%992%EF%BC%88sin%CE%B1%EF%BC%89%5E2+%2B+4sin%CE%B1cos%CE%B1+-+9%EF%BC%88cos%CE%B1%EF%BC%89%5E2%3D%3FA.+3+B.+21%2F10+C.1%2F3+D.1%2F302.%E5%B7%B2%E7%9F%A5sin2%CE%B1%3D-4%2F5+%CE%B1%E2%88%88%EF%BC%88-%CF%80%2F4+%2C+%CF%80%2F4%EF%BC%89%2C%E5%88%99sin4%CE%B1%E7%9A%84%E5%80%BC%3FA.24%2F25+B.-24%2F25+C.4%2F5+D.7%2F253.%E5%87%BD%E6%95%B0y%3D%EF%BC%88sinx%EF%BC%89)
6道高一数学填空选择!求帮忙!在线等!1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?A. 3 B. 21/10 C.1/3 D.1/302.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?A.24/25 B.-24/25 C.4/5 D.7/253.函数y=(sinx)
6道高一数学填空选择!求帮忙!在线等!
1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?
A. 3 B. 21/10 C.1/3 D.1/30
2.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?
A.24/25 B.-24/25 C.4/5 D.7/25
3.函数y=(sinx)^2是最小正周期为___(π或2π)的___(奇或偶)函数.
4.若cos2α=3/5 则(sinα)^2 - (cosα)^2 = ?
5.若α是锐角,且sin(α-π/6)=1/3 则cosα的值是?
6.tan70°+ tan50°-√3 tan70°tan50°=?
麻烦大家了!在线等!
6道高一数学填空选择!求帮忙!在线等!1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?A. 3 B. 21/10 C.1/3 D.1/302.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?A.24/25 B.-24/25 C.4/5 D.7/253.函数y=(sinx)
1.tana=sina/cosa=3
sina=3cosa
sina^2+cosa^2=1
cosa^2=1/10
sina^2=9/10
2(sinα)^2 + 4sinαcosα - 9(cosα)^2=2(sinα)^2 +12(cosa)^2-9(cosα)^2=18/10+3/10=21/10
2.
α∈(-π/4 ,π/4)
2α∈(-π/2 ,π/2)
cos2α>0
(sin2α)^2+(cos2α)^2=1
cos2α=3/5
sin4α=2sin2αcos2α=-24/25
选B
3.
y=(sinx)^2在纸上画个图,就看出来了,x∈(π,2π)为正
最小正周期为π
(sin-x)^2=sina^2
为偶函数,关于Y轴对称
4.
sina^2=(1-cos2a)/2
cosa^2=(1+cos2a)/2
sina^2-cosa^2=1-cos2a=1-3/5=4/5
5.
α是锐角,sina,cosa>0
sin(α-π/6)=sinacos(π/6)-cosasina(π/6)=1/3
((3)^1/2)sina-1/2cosa=1/3
((3)^1/2)为3的平方根,我打不出来根号.
sina^2+cosa^2=1
sina^2=1/12
cosa^2=11/12
你自己开下平方根吧.
6.我忘了tan的性质能说下不,
1.1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?(B)
A. 3 B. 21/10 C.1/3 D.1/30
2.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?(B)
A.24/25 B.-24/25 C.4/5 D.7/25
3.函数y=(sinx)^2是最小正周期为_π__(π或2π)...
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1.1.已知tanα=3 则2(sinα)^2 + 4sinαcosα - 9(cosα)^2=?(B)
A. 3 B. 21/10 C.1/3 D.1/30
2.已知sin2α=-4/5 α∈(-π/4 , π/4),则sin4α的值?(B)
A.24/25 B.-24/25 C.4/5 D.7/25
3.函数y=(sinx)^2是最小正周期为_π__(π或2π)的_奇__(奇或偶)函数。
4.若cos2α=3/5 则(sinα)^2 - (cosα)^2 = ?(-3/5)
5.若α是锐角,且sin(α-π/6)=1/3 则cosα的值是?(-1+2√6)/6
6.tan70°+ tan50°-√3 tan70°tan50°=?(-√3)
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