Taylor series with summation notation

In summary, the conversation is about finding the correct identity to use for the given function f(x) = (1-cos(x^2))/x^3 and tips for solving this type of question. The suggestion is to use the Taylor series for cos x, but since there is an x^3 in the denominator, the x can be placed inside or outside the sum. An example is given for a similar function involving sin 2x^3.
  • #1
myusernameis
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Homework Statement



f(x) = [tex]\frac{1-cos(X^2)}{x^3}[/tex]

which identity shoud i use?
and tips on this type of questions? once i can separate them, then i'll be good


thanks!
 
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  • #2
Do you know a Taylor series for [itex]\cos x[/itex]?
 
  • #3
benorin said:
Do you know a Taylor series for [itex]\cos x[/itex]?

yeah, but there's a x^3 on the bottom...
 
  • #4
Sure, but the summation isn't over x so you can put the x in the sum or outside the sum.
 
  • #5
Example:

[tex]\frac{1-\sin 2x^3}{x}=\frac{1-\sum_{k=0}^{\infty}\frac{\left( 2x^3\right)^{2k+1}}{(2k+1)!}}{x} = {\scriptstyle \frac{1}{x}}-{\scriptstyle \frac{1}{x}}\sum_{k=0}^{\infty}\frac{2^{2k-1}x^{6k+3}}{(2k+1)!}[/tex]
= {\scriptstyle \frac{1}{x}}-\sum_{k=0}^{\infty}\frac{2^{2k-1}x^{6k+2}}{(2k+1)!}[/tex]​
 

1. What is a Taylor series with summation notation?

A Taylor series with summation notation is a mathematical representation of a function as an infinite sum of terms. It is used to approximate a function by adding together simpler functions, and is often written using the summation symbol ∑.

2. How is a Taylor series with summation notation calculated?

A Taylor series with summation notation is calculated using the derivatives of a function. The general formula is ∑(fn(a)/n!)(x-a)n, where n is the order of the derivative, a is the point of expansion, and x is the variable.

3. What is the purpose of using a Taylor series with summation notation?

The purpose of using a Taylor series with summation notation is to approximate a function with a simpler, easier to work with function. This can be useful for solving problems in physics, engineering, and other fields that involve complex mathematical functions.

4. Can a Taylor series with summation notation be used for any function?

No, a Taylor series with summation notation can only be used for functions that are infinitely differentiable at the point of expansion. If a function is not infinitely differentiable, the Taylor series will not accurately approximate the function.

5. Are there any limitations to using a Taylor series with summation notation?

Yes, there are limitations to using a Taylor series with summation notation. As the number of terms in the series increases, the accuracy of the approximation also increases. However, this also means that more terms must be calculated, making the process more time-consuming. Additionally, the Taylor series may not always converge to the original function, so it is important to check for convergence before using the series.

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