填空题 设f(x,y)=sin(xy 2 ),则df(x,y)= 1
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【正确答案】 1、{{*HTML*}}正确答案:y 2 cos(xy 2 )dx+2xycos(xy 2 )dy    
【答案解析】解析:df(x,y)=cos(xy 2 )d(xy 2 ) =cos(xy 2 )(y 2 dx+2xydy) =y 2 cos(xy 2 )dx+2xycos(xy 2 )dy.