Limit of a trigonometric function

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Discussion Overview

The discussion revolves around evaluating limits of trigonometric functions, specifically focusing on the limits as \(x\) approaches infinity and zero. Participants explore relationships between different limit expressions involving the sine function.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Some participants inquire about the limits \(\lim_{x\rightarrow \infty }x\cdot \sin(x)\), \(\lim_{x\rightarrow 0 }\frac{\sin(x)}{\sqrt{x}}\), and \(\lim_{x\rightarrow \infty }\frac{\sin(x)}{x}\).
  • There is a suggestion that the second and third limits may be related to the known limit \(\lim_{x\rightarrow 0 }\frac{\sin(x)}{x}\), though the method of conversion is unclear to some participants.
  • A hint is provided regarding the third limit, stating that the product of a function approaching 0 with a bounded function must have a limit of 0.
  • One participant questions whether the same reasoning applies to the first limit, but another participant argues against it, stating that neither function approaches 0.
  • There is a consideration regarding the oscillatory nature of the first limit, leading to a suggestion that it may not have an infinite limit.

Areas of Agreement / Disagreement

Participants express uncertainty about the limits, with some agreeing on the relationships between certain limits while disagreeing on the application of reasoning to the first limit. The discussion remains unresolved regarding the limits' evaluations.

Contextual Notes

Participants have not reached consensus on the application of known limits to the new expressions, and there are unresolved questions about the behavior of the functions involved.

Yankel
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Hello all,

I need some guidance in solving these limits:

\[\lim_{x\rightarrow \infty }x\cdot sin(x)\]

\[\lim_{x\rightarrow 0 }\frac{sin(x)}{\sqrt{x}}\]

\[\lim_{x\rightarrow \infty }\frac{sin(x)}{x}\]

I guess that the second and third ones are somehow related to

\[\lim_{x\rightarrow 0 }\frac{sin(x)}{x}\]

But I am not sure how to convert the known limit into the new ones.

Thank you in advance.
 
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Yankel said:
Hello all,

I need some guidance in solving these limits:

\[\lim_{x\rightarrow \infty }x\cdot sin(x)\]

\[\lim_{x\rightarrow 0 }\frac{sin(x)}{\sqrt{x}}\]

\[\lim_{x\rightarrow \infty }\frac{sin(x)}{x}\]

I guess that the second and third ones are somehow related to

\[\lim_{x\rightarrow 0 }\frac{sin(x)}{x}\]

But I am not sure how to convert the known limit into the new ones.

Thank you in advance.

Hint for the third: The product of a function that goes to 0 with a bounded function must have a limit of 0.
 
I see. Can I use the same logic in the first as well ?
 
Yankel said:
I see. Can I use the same logic in the first as well ?

No, neither function goes to 0.

As for whether the function has an infinite limit, as it oscillates I would lean towards no...
 

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