高等数学,例2全微分,这题怎么做呢,可以写出详细过程吗?大神

如题所述

例1:z = x^y, z'<x> = yx^(y-1), z'<y> = x^ylnx
dz = z'<x>dx + z'<y>dy = yx^(y-1) dx + x^ylnx dy
例2:z = arctan[(x+y)/(x-y)]
z'<x> = {[(x-y) - (x+y)]/(x-y)^2}/[1+(x+y)^2/(x-y)^2]
= -2y/[(x-y)^2+(x+y)^2] = -y/(x^2+y^2)
z'<y> = {[(x-y) + (x+y)]/(x-y)^2}/[1+(x+y)^2/(x-y)^2]
= 2x/[(x-y)^2+(x+y)^2] = x/(x^2+y^2)
dz = (-ydx+xdy)/(x^2+y^2)
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