Use taylor's THeorem to determine the accuracy

In summary, the conversation discusses the use of Taylor's Theorem to determine the accuracy of an approximation for cos(.3). The speaker initially uses (.3)^4 / 4! to get an approximation of 2.03e-10, but the answer should have been R<=2.03e-5. After further discussion, it is determined that the correct form of the remainder term is actually (.3)^5 / 5! and the error involves f^(n+1)(x) for some number between 0 and c (here .3). The largest possible value of f^(n+1)(x) between 0 and c is used to get an upper bound on the error, which is determined to
  • #1
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Use taylor's THeorem to determine the accuracy of the approximation: cos(.3) ~=1 - (.3)^2 / 2! + (.3)^4 / 4! when i use taylors theorem, i use (.3)^4 / 4! which gets me 2.03e-10 but the asnwer is R<=2.03e-5
 
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  • #2


(.3)^4/4! is not equal to 2.03e-10. What form of the remainder term are you using?
 
  • #3


Okay, it should be (.3)^5 / 5!
 
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  • #4


But i still don't get it, why did i get hte right answer and ignore the f^(n+1)(c) of the formula? (Lagrange error bound) The derivative should have been cos , so i must have picked cos 0. Why?
 
  • #5


The error does NOT involve f^(n+1)(c). It involves f^(n+1)(x) for some number between 0 and c (here .3). Since you don't know that number, you use the largest possible value of f^(n+1)(x) between 0 and c to get an upper bound on the error. Since cosine is decreasing, its largest value is cos(0)= 1.
 

1. What is Taylor's Theorem and how is it used to determine accuracy?

Taylor's Theorem is a mathematical tool used to approximate a function using a series of polynomial terms. It can be used to determine the accuracy of an approximation by comparing it to the actual value of the function at a given point.

2. Can Taylor's Theorem be used for any type of function?

Yes, Taylor's Theorem can be used for any differentiable function, meaning it has a continuous derivative. It is most commonly used for polynomial functions, but can also be used for trigonometric, exponential, and logarithmic functions.

3. How is the accuracy of an approximation determined using Taylor's Theorem?

The accuracy of an approximation using Taylor's Theorem is determined by the number of terms used in the polynomial expansion. The more terms used, the more accurate the approximation will be.

4. Are there any limitations to using Taylor's Theorem?

Yes, there are limitations to using Taylor's Theorem. It can only be used for functions with a continuous derivative, and it may not always provide an accurate approximation for all values of x. In addition, the more terms used in the expansion, the more complex the calculation becomes.

5. How does Taylor's Theorem compare to other methods of determining accuracy?

Taylor's Theorem is often considered more accurate than other methods, such as linear or quadratic approximations, because it uses a series of polynomial terms to approximate the function. However, it may not always be the most efficient method, as it can become more complex with a larger number of terms used in the expansion.

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