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I am given $u=\frac{x+y}{\sqrt 2}$ and $v=\frac{x-y}{\sqrt2}$, how would I find $\frac{d^2}{du^2},\frac{d^2}{dv^2}$?

I rearranged $u$ and $v$ in terms of $x$ and $y$, and I get $x = \frac{u + v}{\sqrt{2}}$ and $y = \frac{u - v}{\sqrt{2}}$. But how do I find $\frac{d^2}{du^2}$ and $\frac{d^2}{dv^2}$?

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    Thanks, so is the answer for both, $0$?2012-01-16
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    What are you differentiating in this expression: $\frac{d^2}{dv^2}$?2012-01-16
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    @Emmad: It doesnt state anything in the problem, although you can take a look at the original question below (note the $v$ changes to $w$ in the original question). http://math.stackexchange.com/questions/99608/change-of-variables-of-pde2012-01-16
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    sorry this is not too advanced for me :)2012-01-16
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    haha no problem, its ok.2012-01-16

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