помогите решить 29 номер

29
1.  z=arctg(x+y)(1-xy)   z'x=1/(1+((x+y)(1-xy))*[(x+y)(1-xy)]'x
[(x+y)(1-xy)]'x=(u'v+v'u)=u=x+y  u'=1   v=1-xy  v'=-y=(1-xy)+(-y*x-y)
z'x=[(1-xy)+(-y*x-y)]/(1+((x+y)(1-xy))

z'y=1/(1+((x+y)(1-xy))*[(x+y)(1-xy)]'y
[(x+y)(1-xy)]'y=u=x+y  u'=1   v=1-xy  v'=-x=[(1-xy)+(-y*x-x)]
z'y=[(1-xy)+(-y*x-x)]/(1+((x+y)(1-xy))

2. z=(ln(x-y))+2arccosy/(x-y)
    z'x=2ln(x-y)*1/(x-y)*2x-2/(1-y/(x-y))*[y/(x-y)]'x
[y/(x-y)]'x=[y*(x-y)^(-1/2)]'x=-1/2*(x-y)^(-3/2)
z'x=2ln(x-y)*1/(x-y)*2x-2/(1-y/(x-y))*[-1/2*(x-y)^(-3/2)]
z'y=-4ln(x-y)*1/(x-y)*2y - 2/(1-y/(x-y))[y/(x-y)]'y
[y/(x-y)]'y=u=y   u'=1/2y   v=(x-y)  v'y=-1/2(x-y) =
=1/(x-y)*[(x-y)/2y+y/2(x-y)]
z'y=-4ln(x-y)*1/(x-y)*2y - 2/(1-y/(x-y))[(x-y)/2y+y/2(x-y)]