Solve Cosine IND Limit Without L'Hospital

In summary, the limit of (1-cos(1-cosx))/(3x^4) as x approaches 0 can be solved using l'Hopital's rule or the Taylor series expansion of cos(x) around x=0. The fourth derivative of the numerator can be calculated using WolframAlpha, and plugging in x=0 gives 3 as the numerator, resulting in a limit of 1/24.
  • #1
Hernaner28
263
0
It's the following one:

[tex]\displaystyle\lim_{x \to{0}}{\frac{1-\cos(1-\cos x)}{3x^4}}[/tex]

In case we have to apply L'Hospital, appart from it, how could I solve this without it?
Thanks!
 
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  • #2
You could use the Taylor series expansion of cos(x) around x=0.
 
  • #3
Mmm I haven't learned Taylor series expansions yet. So anyway, could you tell me how to apply L'Hospital here? There are a lot of steps! I keep getting indeterminations. I cannot figure it out yet...
Thanks for the reply :)
 
  • #4
Hernaner28 said:
Mmm I haven't learned Taylor series expansions yet. So anyway, could you tell me how to apply L'Hospital here? There are a lot of steps! I keep getting indeterminations. I cannot figure it out yet...
Thanks for the reply :)

If you don't have Taylor series yet, then you'll probably want to stick with l'Hopital. But the idea is to use cos(x)=1-x^2/2!+ terms of higher order in x. It does make things easier.
 
  • #5
Sorry but I didn't understand the idea.. could you explain the first steps of the resolution? I keep getting IND 0/0 -- I know I've got to apply l'Hopitale every time I get the indtermination but there're just too many.. it never ends.
 
  • #6
Hernaner28 said:
Sorry but I didn't understand the idea.. could you explain the first steps of the resolution? I keep getting IND 0/0 -- I know I've got to apply l'Hopitale every time I get the indtermination but there're just too many.. it never ends.

l'Hopital will end at the fourth derivative. It has to. Then the denominator becomes a constant. It is a little hard to keep track of the numerator, I will admit.
 
  • #7
Yo just plug that mofo numerator equation into WolframAlpha:
http://www.wolframalpha.com/input/?i=fourth+derivative+of+1-cos(1-cosx)

I agree, it's a nasty numerator, but you can just plug in x = 0 now. Looking at it real quick, and it's looks like the numerator at 0 equals 3, so the limit is 3.

Edit: Oh wait, the limit wouldn't be 3, it would 3/(3*4*3*2*1) = 1/24
 

FAQ: Solve Cosine IND Limit Without L'Hospital

1. What is the cosine IND limit?

The cosine IND limit is a mathematical concept used to determine the behavior of a function as it approaches a certain value. It is commonly used in calculus to solve for the limit of a trigonometric function, such as cosine.

2. What is L'Hospital's rule?

L'Hospital's rule is a mathematical theorem that states that the limit of a fraction of two functions is equal to the limit of the derivatives of those functions, under certain conditions. It is often used to solve for limits that would otherwise be indeterminate.

3. How do I solve cosine IND limit without using L'Hospital's rule?

To solve cosine IND limit without using L'Hospital's rule, you can use other techniques such as evaluating the limit using trigonometric identities or using a graphing calculator to visualize the behavior of the function near the limit. You can also use Taylor series or other approximation methods.

4. Can the cosine IND limit always be solved without L'Hospital's rule?

No, not all cosine IND limits can be solved without L'Hospital's rule. In some cases, using L'Hospital's rule is the most efficient and accurate method of finding the limit. It is important to assess the difficulty of the limit and choose the appropriate method for solving it.

5. What are some common mistakes when solving cosine IND limit without L'Hospital's rule?

Some common mistakes when solving cosine IND limit without L'Hospital's rule include using incorrect trigonometric identities, forgetting to consider the behavior of the function near the limit, and not using proper algebraic techniques to simplify the expression. It is important to carefully check your work and consider multiple approaches when solving limits.

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