已知cos(x-派/4)=根号2/10,x属于(派/2,3派/4).(1)求sinx的值:(2) 求sin(2x+派/3)的值.
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![已知cos(x-派/4)=根号2/10,x属于(派/2,3派/4).(1)求sinx的值:(2) 求sin(2x+派/3)的值.](/uploads/image/z/14287532-68-2.jpg?t=%E5%B7%B2%E7%9F%A5cos%28x-%E6%B4%BE%2F4%29%3D%E6%A0%B9%E5%8F%B72%2F10%2Cx%E5%B1%9E%E4%BA%8E%28%E6%B4%BE%2F2%2C3%E6%B4%BE%2F4%29.%281%29%E6%B1%82sinx%E7%9A%84%E5%80%BC%EF%BC%9A%282%29+%E6%B1%82sin%282x%2B%E6%B4%BE%2F3%29%E7%9A%84%E5%80%BC.)
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已知cos(x-派/4)=根号2/10,x属于(派/2,3派/4).(1)求sinx的值:(2) 求sin(2x+派/3)的值.
已知cos(x-派/4)=根号2/10,x属于(派/2,3派/4).(1)求sinx的值:(2) 求sin(2x+派/3)的值.
已知cos(x-派/4)=根号2/10,x属于(派/2,3派/4).(1)求sinx的值:(2) 求sin(2x+派/3)的值.
因为,cos(x-派/4)=根号2/10,x属于(派/2,3派/4)
所以,
cos(x)cos(派/4)+sin(x)sin(派/4)=根号2/10
cos(x)+sin(x)=1/5
所以,
sin(x)=4/5
cos(x)=-3/5
sin(2x)=-24/25
cos(2x)=-7/25
sin(2x+派/3)
=sin(2x)*根号3/2+cos(2x)*1/2
=-12/25*根号3-7/50
还有什么不明白的地放在问我.