设 u = arcsin (x)/(sqrt(x^2 + y^2)) 则 (partial u)/(partial x) = ____。

设 r = sqrt(x^2 + y^2), u = f(r), 其中 f 具有二阶连续导函数, 则 (partial^2 u)/(partial x^2) +

2.设 (xy,x+y)=(x)^2+(y)^2+xy (其中, =xy =x+y), 则 dfrac (partial f)(partial u)+dfrac

若z=f(x,y),x=u+v,y=u-v,则(partial^2z)/(partial upartial v)=(partial^2z)/(partial x

设 z = (u)/(x+y)，而 u = e^xy，则 (partial z)/(partial y) = ()A. $\frac{xe^{xy}}{x+y}

设 z = e^u sin v，而 u = xy，v = x + y，则 (partial z)/(partial x) = ( )A. $z = e^{xy}

设z=sin(uv)，u=x+y，v=x-y，则(partial z)/(partial y)=【】 设$z=\sin(uv)$，$u=x+y$，$v=x-y

殳 =(u)^2ln v =dfrac (y)(x), =2x-3y,-|||-则 dfrac (partial z)(partial y)= ()-|||-A

=f(x,xy), 则 dfrac (partial u)(partial y)=

13.17 设函数 =f(ln sqrt ({x)^2+(y)^2}) 有二阶连续偏导数,满足 dfrac ({partial )^2u}(partial {x

设f(u)可导，z=xyf((y)/(x))，若x(partial z)/(partial x)+y(partial z)/(partial y)=xy(lny