f(x)=(cos2x-1)*cosxcosx 化简

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f(x)=(cos2x-1)*cosxcosx化简f(x)=(cos2x-1)*cosxcosx化简f(x)=(cos2x-1)*cosxcosx化简f(x)=(1-2sin²x-1)cos

f(x)=(cos2x-1)*cosxcosx 化简
f(x)=(cos2x-1)*cosxcosx 化简

f(x)=(cos2x-1)*cosxcosx 化简
f(x)=(1-2sin²x-1)cos²x
=-2sin²cos²x
=-1/2*(2sinxcosx)²
=-1/2*sin²2x

f(x)=(1-2sin²x-1)cos²x
=-2sin²cos²x
=-1/2*(2sinxcosx)²
=-1/2*sin²2x =-1/2*((1-cos4x)/2)=-1/4(1-cos4x)=1/4cos4x-1/4