# partial differential

Discussion in 'Math' started by eggtree, Jul 26, 2007.

1. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
f(x,y)=x2 In( (3 y2 2x)

= [x2 a/ax In(3 y2-2x)+In(3 y2 -2x) a/ax x2]dx + [x2 *1/3 y2-2x a/ay(3 y2 - 2x)]dy

why is solving dx and dy different ?Not symm matter?

2. ### cumesoftware Senior Member

Apr 27, 2007
1,330
11
It does. When derivating in terms of x, you consider y as a constant. When derivating in terms of y, you consider x as a constant. Hence two different results.

3. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
when differienting dy, x is treated as a constant, that means all x value remain unchange?

4. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Essentially yes. The differential rules that apply to x in this instance are as those that you would apply to a constant.

Dave

5. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
Can I know how was dy work out.I mean the working. I am still a little confused.Pls enlight.Thanks.

I have scan a copy of the question but seem like the there is some error in here. I not able to upload file.

6. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Sure, but can I ask that you write up the original formula so that it reads correctly?

f(x,y)=x2 In( (3 y2 2x)

The bit inside the bracket makes little sense as it is written above.

Dave

7. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
I have actually scan the orginal page but I not able to load it...is there a special way to do it?

8. ### Dave Retired Moderator

Nov 17, 2003
6,960
145

Scroll down to Manage Attachments and click on the button - this will launch a new window/tab from where you can select and upload you image.

Dave

9. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
The safety pin like icon is not highlighted when pointing the curser at it.There is also a message at the bottom left hand side saying: Done,but with error on page .

10. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Don't use the 'safety pin', use the 'Manage Attachments' button on the Additional Options section below the Reply to Thread section.

Additionally, the error is an issue at the client side. Do you have another web browser you can use to see if you upload the image?

Dave

11. ### recca02 Senior Member

Apr 2, 2007
1,211
0
yup, use mozilla fire fox .
this aint a spam

12. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
Sorry for my case, there is no manage attachment on the additional options section.I couldn't find it.

13. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Here is a screen shot that shows the "Manage Attachments" button in the "Additional Options" panel that is available when you use the standard "Post Reply" feature. The "Quick Reply" feature does not have this function.

hgmjr

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Apr 2, 2007
1,211
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15. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
My screen do not have the feature of what you have made a circle on it.No Manage attachment button available.

16. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
eggtree,

Firstly, can you firstly clarify what browser you are using? And what if any add-ons, extensions that you are using (e.g. ad-blockers etc).

Secondly, can you go to:

- UserCP (top-left)
- Edit Options (on left)

Scroll to the bottom - Miscellaneous Options - and check that your Message Editor Interface is set to either the "Standard Editor" or "Enhanced Interface". If not, change it to one of the options and save your settings. Does this help?

Dave

17. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
I have tried to change the setting but it did not work.So I try it attached the file using the pc at my work place.

Here is the file about the math question.Thks.

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18. ### eggtree Thread Starter Member

Nov 28, 2006
27
0
here is another attachment.Thks.

File size:
13 KB
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13