有定义运算x*y=x^2-y^2+2x,则cos(x/3)*sin(x/3)=

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有定义运算x*y=x^2-y^2+2x,则cos(x/3)*sin(x/3)=
有定义运算x*y=x^2-y^2+2x,则cos(x/3)*sin(x/3)=

有定义运算x*y=x^2-y^2+2x,则cos(x/3)*sin(x/3)=
[cos(x/3)]*[sin(x/3)]
=cos²(x/3) -sin²(x/3) +2cos(x/3)
=cos(2x/3) +2cos(x/3)