Multivariable Calculus: When to use Squeeze Theorem to solve limits?

In summary, the conversation discusses the use of squeeze theorem to determine the limit of the given expression. While the textbook states that the limit does not exist, the use of squeeze theorem shows that the limit could potentially be 0. However, there is a concern about other paths not being considered and possibly affecting the result.
  • #1
theBEAST
364
0

Homework Statement


For example in:
lim (x,y) -> (0,0) [(xy^2)/(x^2+y^4)]

This limit does not exist (according to textbook), but if you use squeeze theorem since y^2<(x^2+y^4)
y^2/(x^2+y^4) <= 1 and therefore

0 <= (xy^2)/(x^2+y^4) <= x
as x--> 0
so
lim (x,y) -> (0,0) [(xy^2)/(x^2+y^4)] = 0?
 
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  • #2
What happens if you look at y=sqrt(x)?
 
  • #3
dirk_mec1 said:
What happens if you look at y=sqrt(x)?

I see what you mean but what if i was looking at a different limit and I got 0 every time while using different paths. I still couldn't prove it with squeeze theorem because what if there is just this one path that i never tried.
 

1. What is the Squeeze Theorem in Multivariable Calculus?

The Squeeze Theorem, also known as the Sandwich Theorem, is a powerful tool in Multivariable Calculus that is used to evaluate limits. It states that if two functions, f(x) and g(x), are both approaching the same limit as x approaches a certain value, and if there is a third function, h(x), that is always between f(x) and g(x) near that value, then h(x) will also approach the same limit.

2. When should the Squeeze Theorem be used to solve limits in Multivariable Calculus?

The Squeeze Theorem should be used when a limit cannot be evaluated directly, either because the function is undefined at that point or the limit results in an indeterminate form such as 0/0 or ∞/∞. In these cases, the Squeeze Theorem can help to prove the existence of the limit and determine its value.

3. How do you use the Squeeze Theorem to solve limits in Multivariable Calculus?

To use the Squeeze Theorem, you first need to identify the functions f(x), g(x), and h(x) that are involved in the limit. Then, you need to show that h(x) is always between f(x) and g(x) near the value that x is approaching. Finally, you can evaluate the limit by plugging in the limit value to h(x) and using the limits of f(x) and g(x) to determine the limit of h(x).

4. Can the Squeeze Theorem be used for any type of limit in Multivariable Calculus?

No, the Squeeze Theorem can only be used for limits involving real numbers. It cannot be used for limits involving complex numbers, as the concept of "squeezing" does not apply in the complex plane.

5. Are there any limitations to using the Squeeze Theorem in Multivariable Calculus?

Yes, the Squeeze Theorem can only be used when the limit of h(x) can be easily determined. If the limit of h(x) is also an indeterminate form, then the Squeeze Theorem cannot be used. Additionally, the Squeeze Theorem can only be used when the functions involved are continuous near the value that x is approaching.

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