Can someone give me an intuitive definition for differentials?

In summary, differentials can be defined as the change in the linear approximation for a function for a small change in x. They are often used in calculus and thermodynamics, and can be seen as infinitely small differences. Loomis and Sternberg provide more comprehensive information on the topic in their freely available text, particularly in chapter 3 section 5 and following sections. Knowledge of differentials will be beneficial in future studies.
  • #1
Howers
447
5
Can someone give me an intuitive definition for differentials? My prof said to brush up on them because we'll be seeing them lots in thermo. I don't need all the theory because I'll be seeing them in november in calc. Right now I just have to work with them. Are they just infinitely small differences?
 
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  • #2
read tenenbaum and pollard, ode, first few pages.
 
  • #3
This picture show what differential is for a function f(x)
http://www.bymath.com/studyguide/ana/sec/ana4a.gif
Basically, it is the change in the linear approximation for a function for a change in x, dx.

dy/dx = f '(x) -> differential dy = f '(x) dx
When dx is small dy is a good approximation for f(x + dx) - f(x);
 
  • #4
consider for a smooth curve y=f(x), its family of tangent lines. the differential of f, df, is the family of linear functions whose graphs are those tangent lines.

so that picture depicted the graph of df(x0), the graph of one of the linear functions making up the differential.
 
  • #5
Howers said:
Can someone give me an intuitive definition for differentials? My prof said to brush up on them because we'll be seeing them lots in thermo. I don't need all the theory because I'll be seeing them in november in calc. Right now I just have to work with them. Are they just infinitely small differences?

Loomis and Sternberg, chapter 3 section 5 and following sections.
You'll have to do some preliminary reading in order to get to this point. Their text is freely available.

Even if you don't do more than look at it now, it'll serve you well in November.
 

1. What are differentials?

Differentials are a mathematical tool used to approximate the value of a function at a specific point. They represent the change in the value of a function as one or more of its variables change.

2. How are differentials used?

Differentials are used in calculus to find the slope of a curve at a specific point, as well as to approximate the value of a function at that point. They are also used in optimization problems to find the maximum or minimum values of a function.

3. What is the difference between a differential and a derivative?

A differential is the change in the value of a function, while a derivative is the rate of change of a function. Differentials are represented by the symbol "d" and are used to approximate the value of a function, while derivatives are represented by the symbol "dy/dx" and are used to find the slope of a function at a specific point.

4. How are differentials calculated?

Differentials are calculated using the derivative of a function. The differential of a function f(x) is represented as df(x) and is equal to the derivative of f(x) multiplied by dx (the change in x). This is written as df(x) = f'(x) * dx.

5. Can you give an example of using differentials to approximate a function?

Yes, for example, if we have the function f(x) = x^2 and we want to approximate the value of f(2.5), we can use differentials. The differential of f(x) is df(x) = 2x*dx. So, at x = 2.5, df(x) = 2*2.5*dx = 5*dx. If we let dx = 0.1, then the differential would be 5*0.1 = 0.5. Therefore, the approximate value of f(2.5) would be 0.5 greater than the actual value of f(2.5), which is 6.25. So, f(2.5) ≈ 6.75.

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