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sin3x Cos3x

cos3x=cos(2x+x)=cos2xcosx-sin2xsinx =[(cosx)^2-(sinx)^2]cosx-2sinxcosxsinx =(cosx)^3-(sinx)^2cosx-2(sinx)^2cosx =(cosx)^3-3(sinx)^2cosx sin3x=sin(2x+x)=sin2xcosx+cos2xsinx =2sinxcosxcosx+[(cosx)^2-(sinx)^2]sinx =2sinx(cosx)^2+(...

sin(3x)/sinx +cos(3x)/cosx =[sin(3x)cosx+cos(3x)sinx]/(sinxcosx) =sin(3x+x)/[(1/2)sin(2x)] =2sin(4x)/sin(2x) =4sin(2x)cos(2x)/sin(2x) =4cos(2x)

解: -6sin3xcos3x =-3(2sin3xcos3x) =-3sin6x

利用积化和差公式: sinXsin2Xsin3X = -(1/2)(cos3X-cosX)sin3X 满意请采纳,谢谢!

这是复合函数求导 Sin3x的导数=(sin3x)'=cos3x×(3x)'=3cos3x

这是辅助角公式

2sin3xcos4x=sin(3x+4x)+sin(3x-4x)=sin7x-sinx ∴sin3xcos4x=(sin7x-sinx)/2 =>∫sin3xcos4xdx=∫(sin7x-sinx)/2dx =∫(sin7x)/2dx-∫(sinx)/2dx =-(cos7x)/14+(cosx)/2+C

sinx的导数是cosx,而3x的导数是3,故3和前面的系数消去,得cos3x

何为偶函数:也就是说f(x)=f(-x);将这个带入可得 f(x+t)=f(-x+t) sin(3x+3t)+cos(3x+3t)=sin(-3x+3t)+cos(-3x+3t)其中sin和cos可以互相转换,为了具有可比性,我们需要做一下转换 左边=cos(π/2-3x-3t)+sin(π/2-3x-3t) 右边=cos(-3x+3t)+sin(-3...

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