Find Limit of f(x) w/o L'Hopitals Rule

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SUMMARY

The limit of the function f(x) = [x cos(x)] / [x^3 + 1] as x approaches infinity is determined without using L'Hôpital's Rule. The analysis shows that as x tends to infinity, cos(x) oscillates between -1 and 1, while the denominator x^3 + 1 approaches infinity. Thus, the limit simplifies to (cos(x)/x^2) * (1/(1 + 1/x^3)), which approaches 0 as x approaches infinity. Therefore, the limit of f(x) is conclusively 0.

PREREQUISITES
  • Understanding of limits in calculus
  • Familiarity with trigonometric functions, specifically cosine
  • Knowledge of polynomial behavior as x approaches infinity
  • Basic understanding of L'Hôpital's Rule and its conditions
NEXT STEPS
  • Study the properties of limits involving oscillatory functions
  • Learn about the application of L'Hôpital's Rule and its conditions
  • Explore advanced limit techniques such as the Squeeze Theorem
  • Investigate the behavior of rational functions as x approaches infinity
USEFUL FOR

Students studying calculus, particularly those focusing on limits and trigonometric functions, as well as educators looking for examples of limit evaluation techniques without L'Hôpital's Rule.

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Homework Statement



Find the limit of f(x)=[xcosx]/[x^3 + 1] as x tends to infinity.

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The Attempt at a Solution



Can i use l'hospital's rule here? Or if not, what are the conditions for f(x) to meet so that i may use l'hospital's rule?

Without using l'hop i know that cosx would oscillate between -1 and 1 and that is multiplied by infinity. Then the denominator would tend towards infinity. So what is infinity over infinity?
 
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I think that you don't need L'hopital here.
i.e, if we write it as:
(cos(x)/x^2)*1/(1+1/x^3)->0
as x appraoches infinity, can you see why?
 
yea, thank you!
 

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