prove it for me plz (1 Viewer)

shuning · Apr 19, 2009

nvm me and anna just did it.....

lyounamu · Apr 19, 2009

shuning said:
nvm me and anna just did it.....

lol are you kidding?

i wanted the question

shuning · Apr 19, 2009

回复: Re: prove it for me plz

T.T

ask anna LOL xD i cbf posting it again xD

axlenatore · Apr 19, 2009

shuning said:
nvm me and anna just did it.....

did what eh

annabackwards · Apr 19, 2009

LOL here's the question:

http://i238.photobucket.com/albums/ff62/annabackwards/question.jpg

It's quite straight forward.

axlenatore said:
did what eh

XD

lyounamu · Apr 19, 2009

annabackwards said:
LOL here's the question:

http://i238.photobucket.com/albums/ff62/annabackwards/question.jpg

It's quite straight forward.

XD

lol got it hahha

annabackwards · Apr 19, 2009

lyounamu said:
lol got it hahha

Congrats

I really need to read questions properly. I didn't for a question in my chem and physics 1/2 yearly... so i would've lost a few marks there =="

lyounamu · Apr 19, 2009

annabackwards said:
Congrats

I really need to read questions properly. I didn't for a question in my chem and physics 1/2 yearly... so i would've lost a few marks there =="

there were some algebraic stuff here now and then which got me thinking little bit, otherwise this was a fine question

Drongoski · Apr 19, 2009

If I read yr handwriting correctly:

$\frac{\mathrm{d} }{\mathrm{d} x}cos^{-1}\left (\frac{1-x^{2}}{1+x^{2}} \right )\ \ =\ \ \frac{-\frac{\mathrm{d} (\frac{1-x^{2}}{1+x^{2}})}{\mathrm{d} x}}{\sqrt{1-(\frac{1-x^{2}}{1+x^{2}})^{2}}}\ \ =\ \ \ \frac{-[-2x-2x^{3}-2x+2x^{3}](1+x^{2})}{(1+x^{2})^{2}\sqrt{(1+x^{2})^{2}=(1-x^{2})^{2}}}\\ \\ =\ \ \frac{4x}{(1+x^{2})\sqrt{4x^{2}}}\ \ =\ \ \frac{2}{1+x^{2}}$

Edit:

Hell. I kept making mistakes with LaTeX doing this complex stuff & I took triple the time to type out.

Pwnage101 · Apr 19, 2009

Drongoski said:
If I read yr handwriting correctly:

$\frac{\mathrm{d} }{\mathrm{d} x}cos^{-1}\left (\frac{1-x^{2}}{1+x^{2}} \right )\ \ =\ \ \frac{-\frac{\mathrm{d} (\frac{1-x^{2}}{1+x^{2}})}{\mathrm{d} x}}{\sqrt{1-(\frac{1-x^{2}}{1+x^{2}})^{2}}}\ \ =\ \ \ \frac{-[-2x-2x^{3}-2x+2x^{3}](1+x^{2})}{(1+x^{2})^{2}\sqrt{(1+x^{2})^{2}=(1-x^{2})^{2}}}\\ \\ =\ \ \frac{4x}{(1+x^{2})\sqrt{4x^{2}}}\ \ =\ \ \frac{2}{1+x^{2}}$

Edit:

Hell. I kept making mistakes with LaTeX doing this complex stuff & I took triple the time to type out.

i know eh, im begining to hate LaTex - sure it looks great and neat, but takes too long

annabackwards · Apr 19, 2009

Drongoski said:
If I read yr handwriting correctly:

$\frac{\mathrm{d} }{\mathrm{d} x}cos^{-1}\left (\frac{1-x^{2}}{1+x^{2}} \right )\ \ =\ \ \frac{-\frac{\mathrm{d} (\frac{1-x^{2}}{1+x^{2}})}{\mathrm{d} x}}{\sqrt{1-(\frac{1-x^{2}}{1+x^{2}})^{2}}}\ \ =\ \ \ \frac{-[-2x-2x^{3}-2x+2x^{3}](1+x^{2})}{(1+x^{2})^{2}\sqrt{(1+x^{2})^{2}=(1-x^{2})^{2}}}\\ \\ =\ \ \frac{4x}{(1+x^{2})\sqrt{4x^{2}}}\ \ =\ \ \frac{2}{1+x^{2}}$

Edit:

Hell. I kept making mistakes with LaTeX doing this complex stuff & I took triple the time to type out.

Sorry, my handwritting is quite atrocious and yeah you read it correctly XD

Drongoski · Apr 19, 2009

Pwnage101

LaTeX (based on TeX, developed by the great Stanford computer scientist Donald E Knuth, has been one of the great inventions of the 20th century.) already makes using TeX so much easier. We can't blame LaTeX. How would we post mathematical/scientific formulae without it. I remember doing a rather complex one several times; had to reverse all the way to start again. I cannot find my copy of TeX book now I've begun to be able to use it a little. I know yr pain.

Drongoski · Apr 19, 2009

annabackwards

Those who acknowledge poor handwriting a problem should invite me to show how to write. But almost everyone ignored my suggestion and talked endlessly about which fountain pen to use. It's not too late. Would speed up yr writing. PM if interested.

PS: I did not follow yr handwriting 100%; I dropped the 'y' at the beginning because it should not be there.

shuning · Apr 19, 2009

回复: Re: prove it for me plz

Drongoski said:
If I read yr handwriting correctly:

$\frac{\mathrm{d} }{\mathrm{d} x}cos^{-1}\left (\frac{1-x^{2}}{1+x^{2}} \right )\ \ =\ \ \frac{-\frac{\mathrm{d} (\frac{1-x^{2}}{1+x^{2}})}{\mathrm{d} x}}{\sqrt{1-(\frac{1-x^{2}}{1+x^{2}})^{2}}}\ \ =\ \ \ \frac{-[-2x-2x^{3}-2x+2x^{3}](1+x^{2})}{(1+x^{2})^{2}\sqrt{(1+x^{2})^{2}=(1-x^{2})^{2}}}\\ \\ =\ \ \frac{4x}{(1+x^{2})\sqrt{4x^{2}}}\ \ =\ \ \frac{2}{1+x^{2}}$

Edit:

Hell. I kept making mistakes with LaTeX doing this complex stuff & I took triple the time to type out.

u left sqt x^2 out in the last step xD

Drongoski · Apr 19, 2009

Re: 回复: Re: prove it for me plz

shuning

Shi ma ? wo zhao bu dau.

Isn't sqrt(x^2) = x ?

shuning · Apr 19, 2009

回复: Re: 回复: Re: prove it for me plz

sry i dont speak canto LOL xD
还是应为你的拼音不好？ xD

prove it for me plz (1 Viewer)

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