What is the trick to simplifying the Taylor series of 1/(1 + x^2)?

In summary, the conversation discusses finding a Taylor's series around x=0 and suggests using a pattern in the derivatives to simplify the process. The conversation also mentions two methods for finding the series, expanding in a geometric series or using the Leibniz product rule.
  • #1
animboy
27
0
The equation starts at B and this is my attempt. As you can see it soon complicates and doesn't look like what t should since I already know what the Taylor series of his function should look like. Is there some clever trick to it that I am missing? PS the series is centred around x = 0.

[PLAIN]http://img823.imageshack.us/img823/3459/phys.png
 
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  • #2
A Taylor's series about what central point? Rather than work out a large number of derivatives, I would calculate a few derivatives at the given point and try to find a pattern.

For example, the Taylor's series about x= 0 (the McLaurin series), has f(0)= 1, f'(0)= 0, f''(0)= -2, f'''(0)= 0, f''''(0)= 4!, etc. so I would hypothesize that the nth derivative, at 0, is 0 for odd n, [itex](-1)^n n![/itex] for n odd. Then I would try to prove that is true by induction.
 
  • #3
HallsofIvy said:
A Taylor's series about what central point? Rather than work out a large number of derivatives, I would calculate a few derivatives at the given point and try to find a pattern.

For example, the Taylor's series about x= 0 (the McLaurin series), has f(0)= 1, f'(0)= 0, f''(0)= -2, f'''(0)= 0, f''''(0)= 4!, etc. so I would hypothesize that the nth derivative, at 0, is 0 for odd n, [itex](-1)^n n![/itex] for n odd. Then I would try to prove that is true by induction.

it's at x = 0, I will try your method and post a pic.
 
  • #4
Either write
1/(1+x^2)=1/(1-(-x^2))
and expand in geometric series
or apply Leibniz product rule to
[(1+x^2)/(1+x^2)]
and note
(1+x^2)'''=0
 

1. What is the Taylor series of 1/(1 + x^2)?

The Taylor series of 1/(1 + x^2) is an infinite series expansion that represents the function 1/(1 + x^2) as a sum of terms involving powers of x. It is commonly known as the Maclaurin series since it is centered at x = 0.

2. What is the general formula for the Taylor series of 1/(1 + x^2)?

The general formula for the Taylor series of 1/(1 + x^2) is f(x) = 1 + x^2 + x^4 + x^6 + ... = ∑(n=0 to ∞) x^(2n). This means that each term in the series is given by x raised to an even power, starting with x^0 = 1 and increasing by 2 for each subsequent term.

3. How is the Taylor series of 1/(1 + x^2) useful in mathematics?

The Taylor series of 1/(1 + x^2) is useful in many areas of mathematics, including calculus, complex analysis, and differential equations. It allows for approximating the function 1/(1 + x^2) with a polynomial, which can make it easier to solve problems involving this function.

4. What is the convergence interval of the Taylor series of 1/(1 + x^2)?

The convergence interval of the Taylor series of 1/(1 + x^2) is -1 < x < 1. This means that the series will converge to the function 1/(1 + x^2) for any value of x within this interval. Outside of this interval, the series may not converge or may converge to a different function.

5. How can the Taylor series of 1/(1 + x^2) be used to approximate the value of the function at a given point?

The Taylor series of 1/(1 + x^2) can be used to approximate the value of the function at a given point by plugging in the value of x into the series. The more terms that are included in the series, the more accurate the approximation will be. This method is commonly used in numerical analysis and can be particularly useful when the function is difficult to evaluate directly.

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