F(x+dx)=F(x)+F'(x)dx eqn an identity

  • Thread starter isabella
  • Start date
  • Tags
    Identity
In summary, the conversation discusses an equation that is an approximation of the derivative using the definition of the derivative. It also mentions the Taylor series and the Newton-Rapson algorithm, both of which can be found in a Numerical Analysis textbook. The equation is true when dx is equal to zero and gives an approximation when dx is slightly away from zero.
  • #1
isabella
27
0
F(x+dx)=F(x)+F'(x)dx

is the above eqn an identity or something?can someone explain to me what is happening in this eqn?
 
Last edited:
Physics news on Phys.org
  • #2
It's the approximation which follows from the definition of the derivative

[tex] F'(x)=:\lim_{\Delta x\rightarrow 0} \frac{F(x+\Delta x)-F(x)}{\Delta x} [/tex]

by not considering the limit,but the increment in "x",viz.[itex] \Delta x [/itex],is very,very small (infinitesimal,if you prefer).

Daniel.
 
  • #3
Locate a discussion of Taylor series and the Newton-Rapson algorithm. You'll find a good bit on both in a Numerical Analysis textbook. Now, if you are reading a NA text, and that makes you ask your question, then I am sorry for redirecting you to where you already are. In that case, just notice the obvious.

If dx = 0, then of course f(x+dx) = f(x) + f'(x)dx.

What happens if we move dx slightly away from zero? ...well, see dextercioby's last post.
 
Last edited:

1. What does the equation "F(x+dx)=F(x)+F'(x)dx" mean?

The equation "F(x+dx)=F(x)+F'(x)dx" is an identity in calculus that represents the relationship between a function and its derivative. It states that the value of the function at a point x+dx is equal to the value of the function at x plus the derivative of the function at x, multiplied by the change in x (dx).

2. Why is this equation important in calculus?

This equation is important in calculus because it allows us to calculate the value of a function at a nearby point without having to know the actual function itself. It also helps us understand the relationship between a function and its derivative, which is a fundamental concept in calculus.

3. Can you provide an example of how this equation is used in calculus?

Sure, let's say we have a function f(x) = x^2 and we want to find the value of the function at x = 3. Using the equation "F(x+dx)=F(x)+F'(x)dx", we can calculate the value of the function at x = 3. We know that f'(x) = 2x, so at x = 3, f'(x) = 6. Plugging this into the equation, we get f(3+dx) = f(3) + 6dx. This allows us to approximate the value of the function at x = 3+dx without actually knowing the function itself.

4. Are there any limitations to this equation?

Yes, this equation is only accurate for small values of dx. As dx gets larger, the approximation becomes less accurate. This is why in calculus, we use limits to find the exact value of a function at a point, rather than relying on this equation.

5. How does this equation relate to the concept of the tangent line?

This equation is closely related to the concept of the tangent line, as it allows us to calculate the slope of the tangent line at a point on a curve without knowing the actual function. This is because the derivative of a function represents the slope of the tangent line at any point on the curve. By using this equation, we can approximate the slope of the tangent line without having to find the derivative using the limit definition.

Similar threads

Replies
31
Views
891
Replies
1
Views
908
  • Calculus
Replies
15
Views
1K
Replies
1
Views
904
Replies
8
Views
1K
  • Calculus
Replies
25
Views
1K
Replies
2
Views
1K
Replies
20
Views
2K
  • Calculus
Replies
11
Views
2K
  • Calculus
Replies
4
Views
1K
Back
Top