复合函数的偏导数~~见附件~~谢
设Z=u²v-uv²,而u=xcosy,v=xsiny,求dZ/dy
du/dy = x(-siny) = -v
dv/dy = x(cosy) = u
dZ/dy = d(u²v-uv²)/dy
= [d(u²v)-d(uv²)]/dy
= [u²dv+v(2u)du-v²du-u(2v)dv]/dy
= (u²-2uv)(dv/dy)+(2uv-v²)(du/dy)
= u(u²-2uv) - v(2uv-v²)
= u³+v&...全部
设Z=u²v-uv²,而u=xcosy,v=xsiny,求dZ/dy
du/dy = x(-siny) = -v
dv/dy = x(cosy) = u
dZ/dy = d(u²v-uv²)/dy
= [d(u²v)-d(uv²)]/dy
= [u²dv+v(2u)du-v²du-u(2v)dv]/dy
= (u²-2uv)(dv/dy)+(2uv-v²)(du/dy)
= u(u²-2uv) - v(2uv-v²)
= u³+v³-2uv(u+v)
= (u+v)(u²+v²-3uv)。
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