Definition of derivative

In summary, the difference between lim_{x \rightarrow x_0} f'(x) to exist and for f'(x_0) to exist, definition wise, is that the former requires the function to be continuous at x_0 while the latter does not have this requirement. This can be seen in the example of f(x)= x^2, where the limit of the derivative exists at x=1 but the function is not continuous at that point, therefore making it not differentiable.
  • #1
kittybobo1
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Homework Statement



I had a quick question concerning some definitions. What is the difference between lim_{x \rightarrow x_0} f'(x) to exist and for f'(x_0) to exist, definition wise?

Homework Equations





The Attempt at a Solution

 
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  • #2
If the function is continuous then the limit as x approaches y of f is equal to f evaluated at y. Continunity is not a required property of derivatives (there are examples to show this).
 
  • #3
To take a very simple example, let f(x)= x2 if x is not 1, f(1)= 2. For any x other than 1, f(x)= x2 in some interval around 1 and so it's derivative is 2x. limit as x goes to 1 of f'(x) is 2. But since f(x) is not continuous at x= 1, it is not differentiable there.
 

What is the definition of derivative?

The derivative of a function is a measure of how that function changes as its input changes. It is the slope of the tangent line to the function at a given point.

How do you calculate the derivative of a function?

The derivative can be calculated using the limit definition: f'(x) = lim(h→0) [(f(x+h) - f(x))/h]. This is also known as the difference quotient.

What is the relationship between the derivative and the rate of change?

The derivative of a function at a specific point represents the instantaneous rate of change of that function at that point. This means it tells us how much the function is changing at that exact moment.

What is the importance of derivatives in mathematics and science?

Derivatives are used to find maximum and minimum values of functions, which is important in optimization problems. They are also used to model and analyze rates of change in real-world situations, such as in physics and economics.

Can derivatives be applied to non-linear functions?

Yes, derivatives can be applied to any function, including non-linear functions. They can also be used to find the slope of a curve at any point, not just for straight lines.

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