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

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SUMMARY

The discussion focuses on proving the multivariable limit of the function f(x, y) = [sin²(x − y)] / [|x| + |y|] as (x, y) approaches (0, 0). The limit is established as 0 using the formal definition of a limit, which states that for every ε > 0, there exists a δ > 0 such that ||f(x,y) - f(0,0)|| < ε whenever ||(x,y) - (0,0)|| < δ. Participants emphasize the importance of manipulating the absolute values and applying the epsilon-delta definition effectively to demonstrate the limit's convergence.

PREREQUISITES
  • Understanding of the epsilon-delta definition of limits in multivariable calculus.
  • Familiarity with trigonometric functions, specifically sine and its properties.
  • Knowledge of absolute value functions and their behavior near zero.
  • Basic skills in manipulating algebraic expressions involving two variables.
NEXT STEPS
  • Study the epsilon-delta definition of limits in detail, focusing on multivariable cases.
  • Practice proving limits of functions involving trigonometric expressions.
  • Explore techniques for handling absolute values in limit proofs.
  • Review examples of limits approaching points in two-dimensional space.
USEFUL FOR

Students of calculus, particularly those studying multivariable limits, educators teaching limit concepts, and anyone seeking to strengthen their understanding of limit proofs in two-variable functions.

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:

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

One way to think of it is to start by fixing epsilon and then finding what delta must be (in terms of epsilon).
 

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