Using Chain rule to find derivatives....

In summary, the conversation is discussing finding the derivative of y = (csc(x) + cot(x) )^-1 using the chain rule. The person explains that letting u = csc(x) + cot(x), the derivative can be found by the formula dy/dx = (dy/du)(du/dx). They suggest simplifying u to (1+cos(x))/sin(x) and using the quotient rule to find du/dx.
  • #1
darkknight1
1
0
y = (csc(x) + cot(x) )^-1
Find dy/dx
 
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  • #2
Suppose u = csc(x) + cot x

dy/dx = dy/du × du/dx
 
  • #3
darkknight said:
y = (csc(x) + cot(x) )^-1
Find dy/dx
darkknight, you titled this "using chain rule" and Monoxdifly just told you what that is! Are you able to do this now?

Letting u= csc(x)+ cot(x), y= u^-1. What is dy/du? What is du/dx?
chain rule: dy/dx= (dy/du)(du/dx).

If the difficulty is du/dx, it might help you to write \(\displaystyle u= csc(x)+ cot(x)= \frac{1}{sin(x)}+ \frac{cos(x)}{sin(x)}= \frac{1+ cos(x)}{sin(x)}\) and use the "quotient rule".
 

1. What is the chain rule?

The chain rule is a mathematical rule used to find the derivative of a composite function. It states that the derivative of a composite function is equal to the derivative of the outer function multiplied by the derivative of the inner function.

2. When do you use the chain rule?

The chain rule is used when finding the derivative of a composite function, where one function is nested inside another. It is also used when finding the derivative of a function that is composed of multiple functions.

3. How do you apply the chain rule?

To apply the chain rule, you first identify the outer and inner functions of the composite function. Then, you take the derivative of the outer function and multiply it by the derivative of the inner function. If there are multiple functions, you continue this process until you have the derivative of the entire composite function.

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

Sure, let's say we have the function f(x) = (x^2 + 3)^5. We can rewrite this as f(x) = u^5, where u = x^2 + 3. To find the derivative, we use the chain rule and get f'(x) = 5u^4 * u'. Plugging in u = x^2 + 3 and u' = 2x, we get f'(x) = 5(x^2 + 3)^4 * 2x.

5. Are there any common mistakes when using the chain rule?

Yes, one common mistake is forgetting to take the derivative of the inner function. Another mistake is not properly identifying the inner and outer functions, which can lead to incorrect results. It is important to practice and double check your work when using the chain rule.

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