设f(x,y)=e-xsin(x+2y),则_______.

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问题 设f(x,y)=e-xsin(x+2y),则_______.

选项

答案-2e-xEsin(x+2y)+cos(x+2y)]

解析 [-e-xsin(x+2y)+e-x.cos(x+2y)]=-e-x.cos(x+2y).2-e-x.sin(x+2y).2=-2e-x[sin(x+2y)+cos(x+2y)].
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