Saturday, 11 July 2015

multivariable calculus - Prove the function is not differentiable at (0,0)



Take the function
{f(x,y)=(x2+y2)/sin(x2+y2)when 0<|(x,y)|<π0when (x,y)=(0,0)



I got that this function is differentiable at (0,0). I calculated the partial derivatives at (0,0) of which both were 0 and trying to show the definition of differentiability is not satisfied but I keep getting that it is. Plz help.


Answer




Calculating the partial derivatives at (0,0) you get a limit of the form:



limh0hsin|h|



which does not exist.


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