Proving Convergence Using the Squeeze Theorem: A Brief Guide

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SUMMARY

The discussion focuses on using the Squeeze Theorem to prove that the sequences cos(nπ)/n² and ((-1)ⁿ ln(n))/n² converge to 0. The key steps involve demonstrating that both sequences are bounded by 0 and 1/n², which approaches 0 as n approaches infinity. The participants emphasize the importance of showing work clearly to facilitate assistance in mathematical proofs.

PREREQUISITES
  • Understanding of the Squeeze Theorem in calculus
  • Familiarity with limits, specifically lim 1/n = 0 and lim 1/n² = 0
  • Knowledge of trigonometric functions, particularly cos(nπ)
  • Basic logarithmic properties, especially regarding (-1)ⁿ ln(n)
NEXT STEPS
  • Study the Squeeze Theorem in detail, focusing on its applications in calculus
  • Practice proving limits using the Squeeze Theorem with various sequences
  • Explore the behavior of trigonometric functions in limits, particularly cos(nπ)
  • Investigate the convergence of alternating series and their limits
USEFUL FOR

Students studying calculus, particularly those tackling sequences and series, as well as educators looking for examples of the Squeeze Theorem in action.

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Homework Statement


Use the squeeze theorem to prove the sequence converges to 0. (Given the lim 1/n=0 and 1/n^2=0.

A) cos n pi / n^2

B) ((-1)^n) ln(n) / n^2

I know you have to show that the sequence "squeezes" between the two given above, but I am having problems doing so, any help would be great. Thanks.
 
Last edited:
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denverhockeyfan said:

Homework Statement


Use the squeeze theorem to prove the sequence converges to 0. (Givin the lim 1/n=0 and 1/n^2=0.

A) cos n pi / n^2

B) ((-1)^n) ln(n) / n^2
Although your notation is a little ambiguous i am assuming that on A) you meant

( cos(npi) )/n^2

remember that
0<=Icos(npi)I<= 1, i am assuming also that n is from naturals, than we can safetly multiply by 1/n^2 (or divide by n^2) because it is also positive, (moreover n^2 is always positive regardless of the sing of n) then we get:

0<=Icos(npi)I/n^2 <= 1/n^2 now taking the limit when n--> infinity what do u get?

Next time show your work, before the people here can give you any help.

B) use the same reasoning here also.
 
Last edited:

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