how to make symbols used in differential equations and maths etc character map information needed

[Tapas Mishra]

Hi,
I wanted to know with respect to a link here
http://random.irb.hr/signup.php
if you look at the CAPTCHA section the answer of which it is solution
of a differential equation given.
The answer to the CAPTCHA does not needs any special character map.

But this gave rise to a question in my mind  if there is there some
math library to enter such things.
How can I enter such a mathematical thing in a web form.(The above
link is just an example.)


I googled but http://www.google.co.in/search?sourceid=chrome&client=ubuntu&channel=cs&ie=UTF-8&q=Math+library+for+Ubuntu
the link comes with some C libraries for calculations.
I then checked Gnome Documentation for Character Maps
http://library.gnome.org/users/gucharmap/stable/gucharmap-usage.html.en
but it was not helpful for me.
Then I also checked a page here
http://en.wikipedia.org/wiki/Unicode_typeface#List_of_Unicode_fonts
and one more link
http://computers-technology.helium.com/how-to/12128-how-to-create-special-computer-characters-with-your-keyboard
but not clear as how to put such mathematical symbols which consists
of complex differential equations.What font
do I need to install for typing such characters.

I use Ubuntu 10.04.

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