Maclaurin series of tan (e^x -1)

In summary, the conversation discusses a mathematical problem where the original poster is trying to find the coefficient of x^4 but is getting the wrong answer. They have received help in identifying a mistake in their derivative calculations and have since found the error.
  • #1
delsoo
97
0

Homework Statement




for this, my coefficient of x^4 which is 8/4! = 1/3 .. but the ans should be 13/24... can you tell me which part contain mistake?
https://i.imgur.com/05NnrdM.jpg
https://i.imgur.com/28Q9o51.jpg


Homework Equations





The Attempt at a Solution

 
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  • #2
delsoo said:

Homework Statement




for this, my coefficient of x^4 which is 8/4! = 1/3 .. but the ans should be 13/24... can you tell me which part contain mistake?
https://i.imgur.com/05NnrdM.jpg
https://i.imgur.com/28Q9o51.jpg


Homework Equations





The Attempt at a Solution


In your expression for the third derivative you didn't differentiate the dy/dx factor. You've only got part of the product rule there.
 
  • #3
i redo the question, now my coeffiecient of x becomes only 11 but not 13, now which part is wrong?
https://www.flickr.com/photos/123101228@N03/13809331763/
 
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  • #4
delsoo said:
i redo the question, now my coeffiecient of x becomes only 11 but not 13, now which part is wrong?
https://www.flickr.com/photos/123101228@N03/13809331763/

Exactly the same sort of problem. You left out half of a product rule again. Can't YOU find it? You should have four [...] expressions, not three.
 
Last edited by a moderator:
  • #5
sorry i really can't find it, i have 2 [ ... ] for d3y/dx3 , and i have 4 [...] for d4y/dx4 , can you be more specifiec telling me which part is wrong? thanks!
 
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  • #6
..

...
 
  • #7
delsoo said:
sorry i really can't find it, i have 2 [ ... ] for d3y/dx3 , and i have 4 [...] for d4y/dx4 , can you be more specifiec telling me which part is wrong? thanks!

That's the problem. Yes, you should have four [...]'s for d4y/dx4. In the image you sent, you don't have four. You have three. You are missing one.
 
  • #8
Dick said:
That's the problem. Yes, you should have four [...]'s for d4y/dx4. In the image you sent, you don't have four. You have three. You are missing one.

thanks a lot! i found out i my grave mistake finally!
 
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1. What is a Maclaurin series?

A Maclaurin series is a special type of power series expansion that represents a function as an infinite sum of terms. It is named after the Scottish mathematician Colin Maclaurin.

2. How is the Maclaurin series of tan (e^x -1) derived?

The Maclaurin series of tan (e^x -1) is derived by substituting e^x -1 into the Maclaurin series of tan x and then applying the Maclaurin series for e^x. Simplification and rearrangement of terms results in the final series.

3. What is the general formula for the Maclaurin series of tan (e^x -1)?

The general formula for the Maclaurin series of tan (e^x -1) is ∑(n=1 to ∞) (-1)^(n+1) (2^(2n) - 1) B_(2n) (x^n) / (2n)! where B_(2n) are the Bernoulli numbers.

4. What is the radius of convergence for the Maclaurin series of tan (e^x -1)?

The radius of convergence for the Maclaurin series of tan (e^x -1) is infinite, meaning it converges for all values of x. This is due to the fact that the Maclaurin series for tan x has a radius of convergence of π/2, which is larger than the Maclaurin series for e^x.

5. How is the Maclaurin series of tan (e^x -1) used in real-world applications?

The Maclaurin series of tan (e^x -1) is used in various areas of mathematics and physics, such as in calculating the solution to differential equations, approximating values of functions, and in the study of harmonic analysis. It is also used in computer science and engineering for numerical analysis and optimization problems.

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