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![设fx,fy在点(x0,y0)的某邻域内存在且在点(x0,y0)可微,则有 fxy(x0,y0)=fyx(x0,y0).](https://img2.soutiyun.com/shangxueba/askcard/2023-06/20/947/20230620145609251.jpg)
设fx,fy在点(x0,y0)的某邻域内存在且在点(x0,y0)可微,则有 fxy(x0,y0)=fyx(x0,y0).
设fx,fy在点(x0,y0)的某邻域内存在且在点(x0,y0)可微,则有
fxy(x0,y0)=fyx(x0,y0)。
设fx,fy在点(x0,y0)的某邻域内存在且在点(x0,y0)可微,则有
fxy(x0,y0)=fyx(x0,y0)。
设fx(x,y)在(x0,y0)的某邻域内存在且在(x0,y0)处连续,又fy(x,y)存在,证明f(x,y)在点(x0,y0)处可微
设fx,fy和fyx在点(x0,y0)的某邻域内存在,fyx在点(x0,y0)连续,证明fxy(x0,y0)也存在,且fxy(x0,y0)=fyx(x0,y0).
设函数f(x,y)在点(0,0)的某邻域内有定义,且,则有().
A.
B. 曲面z=f(x,y)在点(0,0,f(0,0))的一个法向量为3i-j+k
C. 曲线在点(0,0,f(0,0))的一个切向量为i+3k
D. 曲线在点(0,0,f(0,0))的一个切向量为3i+k
(1)g(0,0)为何值时,偏导数fx(0,0),fy(0,0)都存在?
(2)g(0,0)为何值时,f(x.y)在点(0,0)处可微分?
A.连续,但不可偏导
B.可偏导但不连续
C.既连续又可偏导,但不可微
D.可微
(1) z=x2-y2,{(x,y)|x2+y2≤4};
(2) z=x2-xy+y2,{(x,y)||x|+|y|≤1};
(3) z=sinx+siny-sin(x+y),{(x,y)|x≥0,y≥0,x+y≤2π}.
(1) f(x,y)=sin(x2+y2)在点(0,0)(到二阶为止);
(2) f(x,y)=ln(1+x+y)在点(0,0);
(3) f(x,y)=2x2-xy-y2-6x-3y+5在点(1,-2).
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