Understanding Derivatives: The Role of the Chain Rule Explained | Homework Help

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In summary, the conversation is about a problem from the speaker's homework involving arcsec and the chain rule. They were confused about why there was an x and not a 2x, but realized their mistake after getting help from someone else. The confusion stemmed from not properly applying the chain rule and bringing down the 1/2 exponent when taking the derivative. The speaker also mentions that they were using arcsec instead of sec^-1x, which they found to be more confusing. The solution involves using the derivative of sec^-1x and applying the chain rule.
  • #1
Puchinita5
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Homework Statement


I attached a problem from my homework.

My only issue is that I don't know why it is x arc sec and not 2x arc sec etc...shouldn't there be a 2x from the chain rule from the derivative inside the square root? I cannot understand for my life why there is an x and not a 2x.

I kept getting this wrong until I googled it and someone in yahoo answers gave a response without a 2, so i tried it and my online homework said it was right. But don't know why!


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  • #2
Well, I didn't get the same result, maybe I have to simplify it, but the 2 factor goes away because the 1/2 exponent "comes down" when you derive sqrt (x^2 - 1). Is that what you are talking about? And why are you talking about arcsec?
 
  • #3
Oh dear. That was a silly mistake! I definitely didn't bring down the 1/2 when I took the derivative. ::slaps forehead:: It's been a while since I took calc 1 so I am making a lot of really silly mistakes now in Calc 2!

I couldn't see for my life what I was missing!

Oh and I was saying arcsec because i thought sec^-1x was more confusing to read.

Thank you for your help!
 
  • #4
1/sec = cos btw
 
  • #5
Well

[tex] (\sec^{-1} x)' = \frac{1}{x\sqrt{x^2 -1}} [/tex]

so that explains the first term. As for the second, there's no 2, because of the chain rule.
 

Related to Understanding Derivatives: The Role of the Chain Rule Explained | Homework Help

1. What is the purpose of the chain rule in understanding derivatives?

The chain rule is a fundamental concept in calculus that allows us to find the derivative of a composite function. This means that we can determine the rate of change of a function that is composed of multiple functions. The chain rule is essential in understanding derivatives because it helps us solve more complex problems and analyze more complicated functions.

2. How do I apply the chain rule to find the derivative of a composite function?

To apply the chain rule, we use the formula: d/dx(f(g(x))) = f'(g(x)) * g'(x). This means that we first find the derivative of the outer function, then multiply it by the derivative of the inner function. It is important to remember that the inner function must be substituted into the derivative of the outer function.

3. Can you provide an example of applying the chain rule to find a derivative?

Sure, let's say we have the function f(x) = (x^2 + 1)^3. To find the derivative, we first identify the outer function, which is (x^2 + 1)^3. The inner function is x^2 + 1. Using the chain rule formula, we have d/dx((x^2 + 1)^3) = 3(x^2 + 1)^2 * 2x. This means that the derivative of f(x) is 6x(x^2 + 1)^2.

4. Why is it important to understand the chain rule when working with derivatives?

The chain rule is essential in solving more complex problems and analyzing more complicated functions. Without understanding the chain rule, we would not be able to find the derivative of composite functions, which are common in many real-world applications. It also helps us understand the relationship between different functions and how changes in one function can affect the overall rate of change.

5. Are there any common mistakes to avoid when using the chain rule to find derivatives?

Yes, there are a few common mistakes to avoid when applying the chain rule. One mistake is forgetting to substitute the inner function into the derivative of the outer function. Another mistake is not applying the chain rule correctly, such as multiplying instead of using the chain rule formula. It is important to carefully follow the steps and double check your work to avoid these errors.

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