How to Solve Trigonometric Limits Using l'Hopital's Rule

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Homework Help Overview

The discussion revolves around evaluating the limit \(\lim_{x\rightarrow0}\frac{x+\sin x}{2x-\sin 3x}\), specifically focusing on the application of l'Hopital's Rule and alternative methods for solving trigonometric limits.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the use of l'Hopital's Rule and inquire about its application, while others suggest dividing terms or using known limits like \(\lim_{x \to 0} \frac{\sin x}{x}\). There are questions regarding familiarity with Taylor series and derivatives, indicating varying levels of understanding among participants.

Discussion Status

The discussion is active, with participants sharing their attempts and seeking clarification on concepts. Some guidance has been offered regarding alternative methods to approach the limit, and there is an ongoing exploration of different interpretations of the problem.

Contextual Notes

Some participants express uncertainty about their knowledge of derivatives and l'Hopital's Rule, indicating that they may not have covered these topics in their studies yet. This suggests a potential gap in foundational understanding that could affect their approach to the problem.

mtayab1994
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Homework Statement



solve the following limit: [tex]\lim_{x\rightarrow0}\frac{x+sinx}{2x-sin3x}[/tex]

The Attempt at a Solution



I know the principle of solving all sorts of limits but not trig limits, and since we just started trig limits it's still not clear to me, but i think to solve it we have to separate it then solve but i don't know. Any help on how to start please?
 
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Do you know l'Hopital's rule?
 
No haven't learned it can you fill me on it please?
 
mtayab1994 said:

Homework Statement



solve the following limit: [tex]\lim_{x\rightarrow0}\frac{x+sinx}{2x-sin3x}[/tex]

The Attempt at a Solution



I know the principle of solving all sorts of limits but not trig limits, and since we just started trig limits it's still not clear to me, but i think to solve it we have to separate it then solve but i don't know. Any help on how to start please?
Are you familiar with Taylor series ?

Added in Edit:

Better yet:
multiply by (1/x) over (1/x) .​
 
mtayab1994 said:
No haven't learned it can you fill me on it please?

You may not have covered it yet so you may be expected to do it a different way. Divide the numerator and denominator by x. Now you probably do know the limit sin(x)/x. Try to use that to find the limits of the terms.
 
SammyS said:
Are you familiar with Taylor series ?

No sorry I'm not familiar with taylor series, but i know that for l'hospital's rule we have to take the derivative of the numerator and the derivative of the denominator; but i have never learned derivatives so i can't do that. Is it possible to solve it some other way?
 
Ok the derivative of x+sinx is cosx+1 and how about the bottom?
 
ok i counted and found the limit to be -2 is that correct?
 
mtayab1994 said:
ok i counted and found the limit to be -2 is that correct?

Yes, if you used l'Hopital then you might check whether that is allowed. Otherwise you should try doing it using that the limit of sin(x)/x is 1.
 
  • #10
Dick said:
Yes, if you used l'Hopital then you might check whether that is allowed. Otherwise you should try doing it using that the limit of sin(x)/x is 1.

Yea thank you very much I get the trick. It's the same for almost all of them.
 

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