已知a是第三象限的角,且f(x)```````已知a是第三象限的角,且f(x)=[sin(π-x)cos(2π-x)tan(-x+3π/2)]/[cos(-x-π)sin(-π-x)](1)化简f(x)(2)若cos(a-3π/2)=1/5,求f(a)的值(3)若a=-1860°,求f(a)的值帮忙写下过程!,谢谢!
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![已知a是第三象限的角,且f(x)```````已知a是第三象限的角,且f(x)=[sin(π-x)cos(2π-x)tan(-x+3π/2)]/[cos(-x-π)sin(-π-x)](1)化简f(x)(2)若cos(a-3π/2)=1/5,求f(a)的值(3)若a=-1860°,求f(a)的值帮忙写下过程!,谢谢!](/uploads/image/z/10129845-21-5.jpg?t=%E5%B7%B2%E7%9F%A5a%E6%98%AF%E7%AC%AC%E4%B8%89%E8%B1%A1%E9%99%90%E7%9A%84%E8%A7%92%2C%E4%B8%94f%28x%29%60%60%60%60%60%60%60%E5%B7%B2%E7%9F%A5a%E6%98%AF%E7%AC%AC%E4%B8%89%E8%B1%A1%E9%99%90%E7%9A%84%E8%A7%92%2C%E4%B8%94f%28x%29%3D%5Bsin%28%CF%80-x%29cos%282%CF%80-x%29tan%28-x%2B3%CF%80%2F2%29%5D%2F%5Bcos%28-x-%CF%80%29sin%28-%CF%80-x%29%5D%281%29%E5%8C%96%E7%AE%80f%28x%29%EF%BC%882%EF%BC%89%E8%8B%A5cos%28a-3%CF%80%2F2%29%3D1%2F5%2C%E6%B1%82f%28a%29%E7%9A%84%E5%80%BC%EF%BC%883%EF%BC%89%E8%8B%A5a%3D-1860%C2%B0%2C%E6%B1%82f%28a%29%E7%9A%84%E5%80%BC%E5%B8%AE%E5%BF%99%E5%86%99%E4%B8%8B%E8%BF%87%E7%A8%8B%21%2C%E8%B0%A2%E8%B0%A2%21)
已知a是第三象限的角,且f(x)```````已知a是第三象限的角,且f(x)=[sin(π-x)cos(2π-x)tan(-x+3π/2)]/[cos(-x-π)sin(-π-x)](1)化简f(x)(2)若cos(a-3π/2)=1/5,求f(a)的值(3)若a=-1860°,求f(a)的值帮忙写下过程!,谢谢!
已知a是第三象限的角,且f(x)```````
已知a是第三象限的角,且f(x)=[sin(π-x)cos(2π-x)tan(-x+3π/2)]/[cos(-x-π)sin(-π-x)]
(1)化简f(x)
(2)若cos(a-3π/2)=1/5,求f(a)的值
(3)若a=-1860°,求f(a)的值
帮忙写下过程!,谢谢!拜托了!明天要交!
已知a是第三象限的角,且f(x)```````已知a是第三象限的角,且f(x)=[sin(π-x)cos(2π-x)tan(-x+3π/2)]/[cos(-x-π)sin(-π-x)](1)化简f(x)(2)若cos(a-3π/2)=1/5,求f(a)的值(3)若a=-1860°,求f(a)的值帮忙写下过程!,谢谢!
1、
f(x)=sinxcosxcotx/[(-cosx)sinx]
=-cotx
2、
cos(a-3π/2)=-sina=1/5
sina=-1/5
第三象限,cosa
Sn=-2n^2-n
S(n-1)=-2(n-1)^2-(n-1)
an=Sn-S(n-1)=-2n^2-n+2(n-1)^2+(n-1)
=2[(n-1)^2-n^2]-1
=-4n+1
a1=-3
an是以-3为首项,-4为公差的等差数列
则a1,a3……,是以-3为首项,-8为公差的等差数列
一共(25-1)/2+1=13项
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Sn=-2n^2-n
S(n-1)=-2(n-1)^2-(n-1)
an=Sn-S(n-1)=-2n^2-n+2(n-1)^2+(n-1)
=2[(n-1)^2-n^2]-1
=-4n+1
a1=-3
an是以-3为首项,-4为公差的等差数列
则a1,a3……,是以-3为首项,-8为公差的等差数列
一共(25-1)/2+1=13项
所以a1+a3+a5 …+a25
=-3*13+(12*13/2)*(-8)
=-39-624
=-663
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