Finding the Taylor Polynomial f4 for sin(2x) at x=pi/4.

In summary, the task is to find the Taylor polynomial f4 for f(x)=sin(2x) at a=pi/4 and to do so, you can use the formula \sum_{n=0}^{\infty} \frac{f^{(n)}(a)}{n!} \cdot (x-a)^{n}. Replacing x with 2x, you get the polynomial ((-1)^n)(2x)^(2n+1)/(2n+1)!) centered at 0. To center it at pi/4, you must derive sin(2x) using the center pi/4, which can be found in the Edwards and Penny Calculus Bible.
  • #1
seto6
251
0

Homework Statement


find the taylor polynomial f4 for f(x)=sin(2x) and a=pi/4


Homework Equations


sin(x)=((-1)^n)(x^(2n+1))/((2n+1)!)



The Attempt at a Solution



so replace x with 2x?
you get ((-1)^n)(2x)^(2n+1)/(2n+1)!)

is this right?
 
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  • #2
seto6 said:

Homework Statement


find the taylor polynomial f4 for f(x)=sin(2x) and a=pi/4


Homework Equations


sin(x)=((-1)^n)(x^(2n+1))/((2n+1)!)



The Attempt at a Solution



so replace x with 2x?
you get ((-1)^n)(2x)^(2n+1)/(2n+1)!)

is this right?

Its a good thing to present it the right way...

You know the formula right?

[tex]\sum_{n=0}^{\infty} \frac{f^{(n)}(a)}{n!} \cdot (x-a)^{n} = \sum_{n=0}^{\infty} \frac{f^{(4)}(\frac{\pi}{4})}{4!} \cdot (x-\frac{\pi}{4})^{4}[/tex]

which you simply expand as show in your Calculus book which then inturn gives the right answer!
 
  • #3
i see i have to center it at pi/4 but this is ((-1)^n)(2x)^(2n+1)/(2n+1)!) centered at 0 so i have to derive it sin(2x) using center pi/4 right

thanks man
 
  • #4
seto6 said:
i see i have to center it at pi/4 but this is ((-1)^n)(2x)^(2n+1)/(2n+1)!) centered at 0 so i have to derive it sin(2x) using center pi/4 right

thanks man

you welcome :) Generally do you have the Edwards and Penny Calculus Bible? You find the whole definition and example in there :)
 

Related to Finding the Taylor Polynomial f4 for sin(2x) at x=pi/4.

1. Why is the Taylor polynomial bad?

The Taylor polynomial is not inherently "bad", but it can sometimes be a poor approximation of a function, especially if the degree of the polynomial is low or the function is highly nonlinear. In these cases, a higher degree polynomial or a different approximation method may be more accurate.

2. Can the Taylor polynomial be used for all functions?

No, the Taylor polynomial can only be used for functions that are infinitely differentiable at a given point. This means that the function must have derivatives of all orders at that point. If the function is not infinitely differentiable, the Taylor polynomial may not be a good approximation.

3. How can I determine the accuracy of a Taylor polynomial?

The accuracy of a Taylor polynomial can be determined by comparing it to the original function. The closer the polynomial is to the function, the more accurate it is. This can be visually assessed by graphing both the polynomial and the function, or by calculating the difference between the values of the polynomial and the function at different points.

4. Are there any alternatives to using the Taylor polynomial?

Yes, there are alternative methods for approximating functions, such as using other types of polynomials (e.g. Chebyshev polynomials), interpolation methods, or numerical integration techniques. The choice of method depends on the specific function and the desired level of accuracy.

5. How can I improve the accuracy of a Taylor polynomial?

The accuracy of a Taylor polynomial can be improved by increasing the degree of the polynomial, using a smaller interval (i.e. using more data points), or using a different approximation method. It is also important to choose a point of expansion that is close to the point at which the function is being approximated.

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