Derivative of a composite function

In summary, when calculating dF(y)/dy, the term (y')^2 can be simplified using the chain rule to 2y' times the derivative of y' which is y''. If you are only differentiating with respect to y, then the derivative is simply 2y.
  • #1
Tensel
7
0
y =f(x), and y'=df(x)/dx, F(y)=y^3+(y')^2
how to deal with the (y')^2 when i calculate dF(y)/dy?
thanks.
 
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  • #2
Do you remember the chain rule? Are you having trouble differentiating that term?
 
  • #3
If u(x) is a fuction of x, then, by the chain rule, the derivative of [itex]u^2[/itex] is 2u times the derivative of u.

If y is a function of x, then the derivative of [itex](y')^2[/itex], with respect to x, is [itex]2y'[/itex] times the derivative of y' which is, of course, y''. That is, the derivative if [itex](y')^2[/itex] is [itex]2y' y''[/itex].
 
  • #4
HallsofIvy, i want to calculate dF(y)/dy, not dF(y)/dx, but you remand me sth. thank you.
 
  • #5
Well, that doesn't require any mention of x at all then! The derivative of [itex]d(y)^2/dy= 2y[/itex].
 
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Related to Derivative of a composite function

1. What is a composite function?

A composite function is a function that is composed of two or more functions. It is created by taking the output of one function and using it as the input for another function.

2. How do you find the derivative of a composite function?

To find the derivative of a composite function, you can use the chain rule. This involves taking the derivative of the outer function and multiplying it by the derivative of the inner function.

3. Can you give an example of finding the derivative of a composite function?

Sure, let's say we have the composite function f(x) = (x^2 + 1)^3. To find the derivative, we would first take the derivative of the outer function, which is 3(x^2 + 1)^2. Then, we would multiply it by the derivative of the inner function, which is 2x. The final derivative would be 6x(x^2 + 1)^2.

4. Are there any shortcuts for finding the derivative of a composite function?

Yes, there are certain cases where you can use shortcuts to find the derivative of a composite function. For example, if the outer function is a logarithmic or exponential function, you can use the logarithmic or exponential rule to find the derivative.

5. Why is it important to understand the derivative of a composite function?

Understanding the derivative of a composite function is important because it allows us to analyze and model more complex functions. It is also a fundamental concept in calculus and is used in many real-life applications, such as physics, engineering, and economics.

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