Product rule in differentiation

In summary, the conversation discusses the steps taken to prove the product rule in mathematical methods for physicists from Riley and Hobson. The participants discuss the definition of the derivative and its application in proving the rule, with one person asking for clarification and the other providing further explanation. The conversation also touches upon the concept of rate of change between two functions.
  • #1
Muthumanimaran
81
2
What has done here in the second line of the proof for product rule?, from Mathematical methods for physicists from Riley, Hobson
they defined f(x)=u(x)v(x) and these steps are given,
I have no idea how to proceed further please help me.
 

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  • #2
Do you know why they bothered to work out ##f(x+\Delta x) - f(x)## at all?
I mean: what's the point?

How would you normally go about proving the product rule - if you didn't have the example from Riley and Hobson?
i.e. do you know the definition of the derivative?
 
  • #3
Simon Bridge said:
Do you know why they bothered to work out f(x+Δx)−f(x)f(x+\Delta x) - f(x) at all?
I mean: what's the point?
I don't know

Simon Bridge said:
How would you normally go about proving the product rule - if you didn't have the example from Riley and Hobson?
i.e. do you know the definition of the derivative?
yes, derivative is the rate of one function to another function, it actually says how fast one function changes with respect to other, am I right?
 
  • #4
yes, derivative is the rate of one function to another function, it actually says how fast one function changes with respect to other, am I right?
Not exactly ... that was the description of what the derivative is, not the definition. The definition is: $$f^\prime(x) = \lim_{\Delta x\to 0}\frac{f(x+\Delta x) - f(x)}{\Delta x}$$ ... this gives the derivative of f(x) with respect to x.

To prove the product rule, first set ##f(x)=v(x)u(x)## then apply the definition to f.
 
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  • #5
Simon Bridge said:
Not exactly ... that was the description of what the derivative is, not the definition. The definition is: $$f^\prime(x) = \lim_{\Delta x\to 0}\frac{f(x+\Delta x) - f(x)}{\Delta x}$$ ... this gives the derivative of f(x) with respect to x.

To prove the product rule, first set ##f(x)=v(x)u(x)## then apply the definition to f.
got it. Thank you
 
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1. What is the product rule in differentiation?

The product rule is a formula used in calculus to find the derivative of a product of two functions. It states that the derivative of the product of two functions is equal to the first function multiplied by the derivative of the second function, plus the second function multiplied by the derivative of the first function.

2. When should the product rule be used?

The product rule should be used when taking the derivative of a function that is a product of two or more functions. It cannot be used for functions that are sums, differences, or quotients.

3. How do you apply the product rule in differentiation?

To apply the product rule, first identify the two functions that are being multiplied together. Then, take the derivative of each function separately. Finally, plug these derivatives into the product rule formula and simplify the resulting expression.

4. Can the product rule be extended to more than two functions?

Yes, the product rule can be extended to any number of functions being multiplied together. The general formula is the derivative of the first function multiplied by the product of the remaining functions, plus the derivative of the second function multiplied by the product of the remaining functions, and so on.

5. What is the purpose of the product rule in differentiation?

The product rule allows us to find the derivative of a product of functions without having to use the limit definition of the derivative. This makes it a more efficient and convenient method for finding derivatives of more complex functions. It is also a fundamental rule in calculus and is used in many applications, such as optimization problems and curve sketching.

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