已知f(x)=【sin(x-3π)cos(2π-x)sin(-x+3π\2)】\【cos(-π-x)sin(-π-x)】1.化简f(x) 2.若x=-31π\3,求f(x)的值
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![已知f(x)=【sin(x-3π)cos(2π-x)sin(-x+3π\2)】\【cos(-π-x)sin(-π-x)】1.化简f(x) 2.若x=-31π\3,求f(x)的值](/uploads/image/z/2624706-18-6.jpg?t=%E5%B7%B2%E7%9F%A5f%28x%29%3D%E3%80%90sin%28x-3%CF%80%29cos%282%CF%80-x%29sin%28-x%2B3%CF%80%5C2%EF%BC%89%E3%80%91%5C%E3%80%90cos%28-%CF%80-x%29sin%28-%CF%80-x%29%E3%80%911.%E5%8C%96%E7%AE%80f%28x%29+2.%E8%8B%A5x%3D-31%CF%80%5C3%2C%E6%B1%82f%28x%29%E7%9A%84%E5%80%BC)
已知f(x)=【sin(x-3π)cos(2π-x)sin(-x+3π\2)】\【cos(-π-x)sin(-π-x)】1.化简f(x) 2.若x=-31π\3,求f(x)的值
已知f(x)=【sin(x-3π)cos(2π-x)sin(-x+3π\2)】\【cos(-π-x)sin(-π-x)】
1.化简f(x) 2.若x=-31π\3,求f(x)的值
已知f(x)=【sin(x-3π)cos(2π-x)sin(-x+3π\2)】\【cos(-π-x)sin(-π-x)】1.化简f(x) 2.若x=-31π\3,求f(x)的值
(1)
f(x)=[sin(x-3π)cos(2π-x)sin(-x+3π/2)]/[cos(-π-x)sin(-π-x)]
=[sin(x-π)cosx(-cosx)]/[cosxsinx]
=sinxcos²x/(cosxsinx)
=cosx
(2)
x=-31π/3
f(x)=cosx=cos(-31π/3)=cos31π/3=cosπ/3=1/2