the partial derivative of f(x,y) with respect to y at the point (xo,yo) is
δf I d I f(xo,yo+h)-f9xo,yo)
----I =----f(xo,y)I =lim ---------------------
δX I(xo,yo) dy Iy=Yo h->0 h
provided the limit exists.
上面的I是一條線的意思
(X零,Y零)
OK 請解釋...
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