Understanding a Step in Finding a Limit: Lim(x->0) x.sqrt(x+2) / sin(x)

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Discussion Overview

The discussion revolves around understanding the limit Lim(x->0) x.sqrt(x+2) / sin(x). Participants explore the reasoning behind the limit of sin(x)/x as x approaches 0 and seek clarification on the steps involved in evaluating the limit.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses confusion about how sin(x)/x approaches 1 as x approaches 0.
  • Another participant notes that the limit of sin(x)/x being 1 is a standard result often derived in calculus courses, typically using the squeeze theorem.
  • A participant suggests using l'Hôpital's rule as an alternative method for finding the limit.
  • Further contributions mention that the limit can also be understood through the derivative of sin at x=0, which equals cos(0) = 1.
  • Some participants share their personal experiences with learning and gaps in knowledge due to non-traditional educational paths.
  • There is a request for additional resources on the definition of limits, indicating a desire for further understanding.

Areas of Agreement / Disagreement

Participants generally agree on the standard result that sin(x)/x approaches 1 as x approaches 0, but there is no consensus on the best method to understand or prove this limit. The discussion remains exploratory with varying levels of understanding and approaches suggested.

Contextual Notes

Some participants mention gaps in their knowledge and express uncertainty about their understanding of limits, indicating that the discussion may involve varying levels of familiarity with calculus concepts.

Who May Find This Useful

Individuals seeking clarification on limits in calculus, particularly those who may have gaps in foundational knowledge or are exploring different methods of understanding limits.

Cal124
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Apologies if this is in the wrong place. I'm struggling to understand a step in finding a limit
Lim(x->0) x.sqrt(x+2) / sin(x)
Following the given solution I get to the point where it's all divided through by x to give
Sqrt(x+2) / sin x/x
Which as approaching 0 gives
Sqrt(2) / 1 = sqrt(2)
I'm struggling how sin x/x is 1
Any help would be great and any advice on limits or links to resources would be appreciated!
 
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The limit as sin x/x approaches 0 being 1 is usually a standard result that's done in calculus 1 courses--i.e. In most courses I've seen, the professor derives that in class, usually using the squeeze theorem, and then the students usually memorize it.

Otherwise, if you know l'Hôpital's rule, then you can use that. I'm not aware of any other methods.
 
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axmls said:
The limit as sin x/x approaches 0 being 1 is usually a standard result that's done in calculus 1 courses--i.e. In most courses I've seen, the professor derives that in class, usually using the squeeze theorem, and then the students usually memorize it.

Otherwise, if you know l'Hôpital's rule, then you can use that. I'm not aware of any other methods.
Thanks! Just clicked into place now, remember him explaining this now. There is some frustrating gaps in my knowledge due to a non traditional route to higher education.
Thanks again!
 
if you know the derivative of sin is cos, then the limit of sin(x)/x as x-->0 is the value of the derivative of sin at x=0, i.e. cos(0) = 1. of course most people prove this using the value of that limit, although there are other approaches, such as defining sin and cos as solutions of a certain differential equation, or by giving their taylor series. my detailed explanation of the limit approach is here:

http://alpha.math.uga.edu/~roy/tangents_to_y.pdf
 
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mathwonk said:
if you know the derivative of sin is cos, then the limit of sin(x)/x as x-->0 is the value of the derivative of sin at x=0, i.e. cos(0) = 1. of course most people prove this using the value of that limit, although there are other approaches, such as defining sin and cos as solutions of a certain differential equation, or by giving their taylor series. my detailed explanation of the limit approach is here:

http://alpha.math.uga.edu/~roy/tangents_to_y.pdf

That's a much easier way to grasp the concept, thanks! Will get reading!
Sorry, I don't suppose you have any advice/similar PDF on the definition of a limit? I feel I'm getting there (although part of me feels it could all be wrong and I'm miles away)
 
Cal124 said:
That's a much easier way to grasp the concept, thanks! Will get reading!
Sorry, I don't suppose you have any advice/similar PDF on the definition of a limit? I feel I'm getting there (although part of me feels it could all be wrong and I'm miles away)

You mean the episilon/delta?
 
MidgetDwarf said:
You mean the episilon/delta?
Yeah
 

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