The Rahul
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Hii please help me to Solve problems diffrentiability of function with two variable with one method.
The Rahul said:Hii Tiny tim,thnx for ur warm welcome,
Now I continue my problem=
In this Ques.—f(x,y)={|xy|}^1/2 Not differentiable at (0,0)
I find out Both Partial derivative fx and fy and solve the ques.
But in that ques.== f(x,y)= xy /√(x^2+y^2)
in my book method is diffrent.
in that ques method is to find according to y=mx and x=y^3.
so Plz help me...:-D
tiny-tim said:Hi The Rahul!
To prove that a function f(x,y) is not differentiable at (0,0),
we only need to find one curve along which it is not differentiable (and then we can stop).
If f(x,y) = xy /√(x2+y2) = xy/r,
then the derivative along any straight line does exist at (0,0), so we can't stop there, we need to check other ways of approaching the origin …
in this case, the easiest curve to check is x=y3 (or y=x3)
(x=y2 is awkward, because it gives you awkward square-roots
btw, since you've woken the mentors, please note that txt-english (eg "please", "ur") is against the forum rules!
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