What Happens When Partial Derivatives of a Function Are Equal?

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SUMMARY

The discussion centers on the implications of equal partial derivatives of a differentiable function. Specifically, if the partial derivatives \(\partial f/\partial x\) and \(\partial f/\partial y\) are equal to a constant \(C\), the function can be expressed as \(f(x,y) = Cx + Cy + C'\), where \(C'\) is an arbitrary constant. This indicates that equal partial derivatives lead to a linear relationship in the function's variables.

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sunrah
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Hi, in general can we tell anything about the partial derivatives of a differentiable function if they are equal?

for example I would like them to have to equal some constant. Would this be true?
 
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Do you mean [itex]\partial f/\partial x= C[/itex] and [itex]\partial f/\partial y= C[/itex]? The same constant or different constants? From [itex]\partial f/\partial x= C[/itex], we get [itex]f(x,y)= Cx+ g(y)[/itex] where g can be any function of y. Differentiating that with respect to y, [itex]\partial f/\partial y= g'(y)= C[/itex] which tells us that g(y)= Cy+ C' where C' is an arbitrary constant of integration. That is, f(x,y)= Cx+ Cy+ C'.
 

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