Proving Multivariable Limit: f(x, y) → 0

karens
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Homework Statement


Consider that f(x, y) = [sin^2(x − y)] / [|x| + |y|].
Using this, prove: lim(x,y)→(0,0) f(x, y) = 0


Homework Equations



Definition of a limit, etc.

The Attempt at a Solution


I don't know how to start... I've been trying to self-teach limits for a while and Don't know how to do it with the absolute values and two variables. Help is much needed.
 
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Start with the definition of a limit:

\forall \epsilon > 0\ \ \ \exists \delta > 0 such that ||f(x,y) - f(x_0,y_0)|| < \epsilon whenever ||(x,y) - (x_0,y_0)|| < \delta.

One way to think of it is to start by fixing epsilon and then finding what delta must be (in terms of epsilon).
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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