Taylor Expansion of f+df About x?

In summary, the conversation discusses the concept of expanding f+df about x and the confusion surrounding its meaning and relationship to x. The individual eventually finds their answer and provides a formula for f+df. They also mention the importance of defining variables in mathematical equations.
  • #1
rexregisanimi
43
6
How would one expand f+df about x? I'm messing something up in the process and can't seem to resolve it lol
 
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  • #2
What does f+df mean?
How are they related to x?

There is way too much context missing to answer that.
 
  • #3
It shouldn't matter; f is a function of x (and other variables)...
 
  • #4
rexregisanimi said:
It shouldn't matter; f is a function of x (and other variables)...

You can't Taylor expand around a variable. You expand around a fixed base point. That's why we write the polynomials terms as ##(x-a)^n##, i.e. expand around a.
 
  • #5
rexregisanimi said:
It shouldn't matter;
It does matter. Letters without any definition are pointless.
It is like asking "what is x+y?" You cannot answer it (apart from "it is x+y") if you have no idea what x and y are.
 
  • #6
Wow...

I was either communicating poorly or something. I found my answer.

f+df = f +(df/dx)dx + (d2f/dx2)dx2 + ... [The parenthetical terms are partials but not the differentials.]

My favorite is, "It does matter. Letters without any definition are pointless." And to think I wasted all that time learning Algebra! :/
 

Related to Taylor Expansion of f+df About x?

1. What is the Taylor Expansion of f+df About x?

The Taylor Expansion of f+df About x is a mathematical technique used to approximate a function f(x) with a polynomial of increasing degree centered at a specific point x. This expansion is useful in finding the values of a function at points near the initial point x.

2. How do you calculate the Taylor Expansion of f+df About x?

The Taylor Expansion of f+df About x can be calculated using the Taylor series formula, which is f(x) = f(x0) + f'(x0)(x-x0) + (1/2!)f''(x0)(x-x0)^2 + (1/3!)f'''(x0)(x-x0)^3 + ... where x0 is the point we are approximating around and f'(x0), f''(x0), and f'''(x0) are the derivatives of the function evaluated at x0.

3. What is the purpose of using the Taylor Expansion of f+df About x?

The purpose of using the Taylor Expansion of f+df About x is to obtain an approximation of a function at a specific point x. This can be useful in situations where it is difficult to find the exact value of a function or when the function is too complex to work with directly.

4. What are some real-world applications of the Taylor Expansion of f+df About x?

The Taylor Expansion of f+df About x is used in various fields such as physics, engineering, and economics. It is used to approximate the behavior of a system or to find the values of functions in these fields. For example, it can be used to approximate the trajectory of a projectile or to predict the growth of a population.

5. What is the difference between Taylor Expansion of f+df About x and Taylor Expansion of f About x?

The Taylor Expansion of f+df About x involves adding a small change (df) to the original function (f) before performing the expansion. This allows for a more accurate approximation of the function at a specific point x. On the other hand, the Taylor Expansion of f About x only uses the original function f and does not take into account any small changes. Therefore, the Taylor Expansion of f+df About x is generally more accurate than the Taylor Expansion of f About x.

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