# Maclaurin series of tan (e^x -1)

1. Apr 12, 2014

### delsoo

1. The problem statement, all variables and given/known data

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

2. Relevant equations

3. The attempt at a solution

2. Apr 12, 2014

### Dick

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. Apr 12, 2014

### delsoo

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/ [Broken]

Last edited by a moderator: May 6, 2017
4. Apr 12, 2014

### Dick

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: May 6, 2017
5. Apr 13, 2014

### delsoo

sorry i really cant 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!!

Last edited: Apr 13, 2014
6. Apr 13, 2014

### delsoo

..

.........

7. Apr 13, 2014

### Dick

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. Apr 13, 2014

### delsoo

thanks a lot! i found out i my grave mistake finally!

Last edited: Apr 13, 2014