Mastering the Chain Rule: A Quick Guide for Calculus Students

In summary, to find dy/dx for the function y = 2x / (1+x^2)^2, both the quotient rule and the chain rule must be used. However, it is also possible to bring the denominator up top and use the product rule for a simpler solution.
  • #1
asd1249jf

Homework Statement


y = 2x / (1+x^2)^2

Find dy/dx

Homework Equations


Chain rule


The Attempt at a Solution


I completely forgot how to apply the chain rule.. I mean, I can always apply the quotient rule, but I'm sure this is 1000 times easier if you can apply the chain rule. Do you do something like

u = 1+x^2
du = 2x

so

y = du/u

But I may be getting confused with substitution rule with integration.. it's been a while since I touched calculus.. any suggestions?
 
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  • #2
Chain rule goes something like
dy/dx=dy/du*du/dv*...*df/dx .

It is usually used when you when you have a nested combination of functions, ie functions within functions.

For your question, you need to use both the quotient rule as well as the chain rule ( (1+x^2)^2, which is the funtion 1+x^2 within a squaring function ) .

Can you finish your problem now ?
 
  • #3
arunbg said:
Chain rule goes something like
dy/dx=dy/du*du/dv*...*df/dx .

It is usually used when you when you have a nested combination of functions, ie functions within functions.

For your question, you need to use both the quotient rule as well as the chain rule ( (1+x^2)^2, which is the funtion 1+x^2 within a squaring function ) .

Can you finish your problem now ?

Right.. that's the BRUTE force way to do it.

I was wondering if there was a way to finish this without even applying the quotient rule
 
  • #4
if you don't want to use the quotient rule you can bring the denominator up top so:[tex] y= 2x (1+x^2)^{-2}[/tex] now use the product rule
 
  • #5
l46kok said:
Right.. that's the BRUTE force way to do it.

I was wondering if there was a way to finish this without even applying the quotient rule

Yes, just write the expression as 2x(1+x2)-2, and use the product rule on this.
 
  • #6
suspenc3 said:
if you don't want to use the quotient rule you can bring the denominator up top so:[tex] y= 2x (1+x^2)^{-2}[/tex] now use the product rule

I guess that's true, but when I saw the relating terms, I was thinking this could be solved by ONLY using chain rule.

I guess it's impossible.
 

1. What is the chain rule in calculus?

The chain rule is a formula used in calculus to find the derivative of a composite function. It allows us to take the derivative of an outer function and multiply it by the derivative of the inner function.

2. Why is the chain rule important?

The chain rule is important because it allows us to find the derivative of more complex functions by breaking them down into smaller, more manageable parts. It is a fundamental concept in calculus and is used in many real-world applications.

3. What is the process for applying the chain rule?

To apply the chain rule, you must first identify the inner and outer functions of the composite function. Then, take the derivative of the outer function and multiply it by the derivative of the inner function, which is found by substituting the inner function into the derivative of the outer function.

4. Can you give an example of using the chain rule?

Sure, let's say we have the function f(x) = (2x^2 + 3)^5. The inner function would be 2x^2 + 3 and the outer function would be x^5. To find the derivative, we would first take the derivative of the outer function, which is 5x^4. Then, we substitute the inner function into this derivative, giving us 5(2x^2 + 3)^4 * 4x = 20x(2x^2 + 3)^4. This is the derivative of the original function f(x).

5. What are some common mistakes when using the chain rule?

Some common mistakes when using the chain rule include forgetting to take the derivative of the outer function, not substituting the inner function into the derivative correctly, and not applying the chain rule to all parts of the function. It is important to double check your work and practice using the chain rule to avoid these mistakes.

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