Find 9th Derivative of f(x) = cos(6x^4)-1 at x=0 | Maclaurin Series Homework

Click For Summary
SUMMARY

The discussion focuses on calculating the 9th derivative of the function f(x) = (cos(6x^4) - 1) / x^7 at x=0 using the Maclaurin series. The key insight is that only the term containing x^9 in the series expansion contributes to the 9th derivative. The Maclaurin series for cos(x) consists of even powers, and the term from cos(6x^4) relevant to this calculation is derived from the fourth power, which results in x^16. Thus, the calculation simplifies to finding the coefficient of x^9 after accounting for the division by x^7.

PREREQUISITES
  • Understanding of Maclaurin series expansion
  • Knowledge of derivatives and their computation
  • Familiarity with trigonometric functions and their series representations
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the Maclaurin series for cos(x) in detail
  • Practice calculating higher-order derivatives of functions
  • Explore the concept of Taylor series and their applications
  • Learn about the significance of even and odd powers in series expansions
USEFUL FOR

Students studying calculus, particularly those focusing on series expansions and derivatives, as well as educators looking for examples of applying Maclaurin series in problem-solving.

demersal
Messages
41
Reaction score
0

Homework Statement




(1 pt) Compute the 9th derivative of:
f(x) = \frac{cos(6x^4)-1}{x^7}
at x=0.



Homework Equations



Hint: Use the MacLaurin series for f(x).

The Attempt at a Solution



I have tried many weird ways and cannot come up with the correct numerical answer. I've gotten 0 each time and it still comes up as wrong. Please help point me in the correct direction, even if it is only a verbal explanation!

Thanks so much
 
Physics news on Phys.org
The only term in the expansion that would contribute to a 9th derivative would be the term containing x^9. If you look up the Maclaurin series of cos you'll it can be written as a sum of even powers of it's argument. The fourth power of 6x^4 contains an x^16. 16-7=9. Is that enough of a hint.
 
Yes, thank you very much. I think I can work it out now!
 

Similar threads

  • · Replies 48 ·
2
Replies
48
Views
6K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K