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ap calc

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Unit 1

1.8 Determining Limits Using the Squeeze Theorem

#limits

#squeezetheorem


written by

Anusha Tekumulla

anusha tekumulla

published on march 24, 2020

Last updated on June 11, 2020

The Squeeze Theorem ๐Ÿฅช

The Squeeze Theorem (or Sandwich Theorem) is used on limit problems where the usual algebraic methods (factoring, conjugation, algebraic manipulation, or trig identities) are not effective. ๐Ÿฅช

The actual Squeeze Theorem states that f(x) โ‰ค g(x) โ‰ค h(x) for all x in an open interval about a. If the limit as x approaches a of f(x) = L and the limit as x approaches a of h(x) = L, then the limit as x approaches a of g(x) = L.

With the Squeeze Theorem, we are trying to find two functions that are 1) similar enough to the original function that we can be sure the squeeze works and 2) easier to evaluate their limit as x โ†’ a. The theorem utilizes the statement โ€œIf two functions squeeze together at a particular point, then any function trapped between them will get squeezed to that same point.โ€ย 

So, in order to use the squeeze theorem on a limit, we just have to find functions similar enough that all three functions squeeze together at a particular point like the image below.ย 

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Fsqueeze-theorem-graph-picture.png?alt=media&token=e49bdf15-7401-4e17-91e1-1f19d7844788

Math Warehouse

If youโ€™re confused, take a look at an example problem using the Squeeze Theorem.ย 

Example Problem ๐Ÿ’ก

As you can see in the image above, while the limit of the function in red may be hard to solve for, the similar functions in purple help us figure out that the limit of the function will still be zero. We can use this as an example.ย 

First, we must confirm that f(x) โ‰ค g(x) โ‰ค h(x). From the graph, we can confirm that f(x) and h(x) โ€œsqueezeโ€ g(x) at x = 0.ย Now we know that f(x) โ‰ค g(x) โ‰ค h(x), the limit as x approaches 0 of f(x)= 0, and the limit as x approaches 0 of h(x) = 0 using the graph. Thus, the limit as x approaches 0 of g(x) IS also equal to 0.

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