Limit Definition of Derivative

In summary, the limit definition of a derivative is a mathematical expression used to calculate the instantaneous rate of change of a function at a specific point. It is important because it allows us to find the rate of change even for non-continuous or non-differentiable functions, and is the basis for many applications of derivatives. To find the derivative using the limit definition, you must find the slope of the secant line and take the limit of the average rate of change as the distance between two points approaches zero. This method is more general than the power rule, which only works for polynomials. The limit definition can also be used to find higher order derivatives by taking the derivative of the derivative.
  • #1
cjaylee
7
0

Homework Statement


Use the limit definition of derivative to determine the derivative of the following function:

f(x) = { sqrt(x^2+1) if x<=0
0 if x>0

Homework Equations



I'm not sure as to why the function is not continuous at x=0, and so it's not differentiable at that point.

The Attempt at a Solution



The left-hand limit and right-hand limit give me 0. And if I plot a graph, the graph hits 0 as it moves from one function to the other.
 
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  • #2
The left hand limit is "1", not "0"! I would think that would be obvious. What is f(-0.001)?
 

What is the definition of the limit of a derivative?

The limit definition of a derivative is the mathematical expression used to calculate the instantaneous rate of change of a function at a specific point. It involves taking the limit of the average rate of change as the interval between two points becomes infinitesimally small.

Why is the limit definition of a derivative important?

The limit definition of a derivative is important because it allows us to calculate the instantaneous rate of change of a function at a specific point, even when the function is not continuous or differentiable. It is also the basis for many applications of derivatives in calculus and real-world problems.

How do you use the limit definition of a derivative to find the derivative of a function?

To use the limit definition of a derivative, you must first find the slope of the secant line between two points on the function. Then, you let the distance between the two points approach zero, taking the limit of the average rate of change to find the instantaneous rate of change, or the derivative, at that specific point.

What is the difference between the limit definition of a derivative and the power rule?

The power rule is a shortcut method for finding derivatives of polynomial functions, while the limit definition of a derivative is a more general approach that can be used for any type of function. The power rule only works for polynomials, while the limit definition can be used for any continuous function.

Can the limit definition of a derivative be used to find higher order derivatives?

Yes, the limit definition of a derivative can be used to find higher order derivatives by taking the derivative of the derivative. For example, the second derivative is found by taking the derivative of the first derivative using the limit definition, and so on for higher order derivatives.

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