Derivative of x^2sin(4x) + xcos^(-2x)

In summary, the conversation discusses using the chain rule to find the derivative of a complex function. One person is unsure of where to start and provides their answer, but another person notes that the work is difficult to read and suggests tidying it up and avoiding confusing notation. The final answer is given as 2xsin4(x)+4x2sin3(x)cos(x)+cos-2(x)+2xcos-3(x)xsin(x).
  • #1
TommG
28
0
Need to find the Derivative using the chain rule

y = x2sin4(x) + xcos-2(x)

I am not sure where to start.

answer in book is
2xsin4(x) + 4x2sin3(x)cos(x) + cos-2(x) +2xcos-3(x) xsin(x)
 
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  • #2
I am not sure if I did it right but I think I got the answer.

x2sin4(x)
2xsin4 took derivative of just x2
4x2sin3x derivative of just power of sin
cosx derivative of just sin

2xsin4(x)+4x2sin3(x)cos(x)

xcos-2(x)

cos-2 derivative of x
-2xcos-3(x) derivative of power of cos
-xsin(x) derivative of just cos

cos-2+2xcos-3(x)sin(x)

final answer
2xsin4(x)+4x2sin3(x)cos(x)+cos-2(x)+2xcos-3(x)xsin(x)
 
Last edited:
  • #3
Yes, but your work is very strange and hard to read, and I think it makes it more difficult than it should be.

Also, tidy up your penmanship a bit. sin² doesn't mean anything.

Just some suggestions.
 

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.

Why is the chain rule important?

The chain rule is important because it allows us to find the derivatives of more complex functions by breaking them down into simpler functions. It is a crucial tool in calculus and is used in many real-world applications.

How do you use the chain rule to find derivatives?

To use the chain rule, you first identify the outer function and the inner function of the composite function. Then, you take the derivative of the outer function and multiply it by the derivative of the inner function, using the chain rule formula.

What is an example of using the chain rule to find a derivative?

For example, to find the derivative of f(x) = (3x^2 + 1)^4, you would first identify the outer function as f(x) = x^4 and the inner function as g(x) = 3x^2 + 1. Then, using the chain rule formula, the derivative would be f'(x) = 4(g(x))^3 * g'(x) = 4(3x^2 + 1)^3 * 6x = 24x(3x^2 + 1)^3.

Can the chain rule be applied to more than two functions?

Yes, the chain rule can be applied to any number of functions in a composite function. You simply take the derivative of each function, multiplying them together as you go. This is known as the generalized chain rule.

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