设z=arctan[(x+y)/(x-y)],则dz=?

来源:学生作业帮助网 编辑:作业帮 时间:2024/12/01 07:16:18
设z=arctan[(x+y)/(x-y)],则dz=?
xRN@/m(^Xv(۲AHIn&)Ĕ*1 P~3c "MgιsGdiT5s> =ٟO#TDjY ci߭ZYtxu/&$`tT,!a@OȴڤӧN~·G%;͞,9w:mL@kUlC(!d8@̕03ےaX&YW!6!Z}ЭhbGu+rKS ʜ+wL>'|R6y$bOƾr zy

设z=arctan[(x+y)/(x-y)],则dz=?
设z=arctan[(x+y)/(x-y)],则dz=?

设z=arctan[(x+y)/(x-y)],则dz=?
此题比较适合利用一阶微分形式不变性,以及微分本身的运算法则求
令 x+y=u,x-y=v,t=(x+y)/(x-y)=u/v 则
dz=d(arctant)=[1/(1+t^2)] dt=[1/(1+t^2)]d[u/v]=[1/(1+t^2)][1/v^2](vdu-udv)
=[1/(1+u^2/v^2)][1/v^2](vdu-udv)=[1/(u^2+v^2)](vdu-udv)
={1/[(x+y)^2+(x-y)^2]}[(x-y)(dx+dy)-(x+y)(dx-dy)]
=[1/(2x^2+2y^2)](-2ydx+2xdy)
用这种方法解这类题目,条理清晰,不易算错,熟悉以后,不需要写出设置中间变量的过程.

dz={[-2y/(x-y)^2]dx +[2x/(x-y)^2]dy}][(x-y)^2/(2x^2+2y^2)]
刚才算错了特此道歉!