What’s the best software for typing mathematics?

I’d like to complete a maths notices on the comp.Yet i dont find all symbolic representation of maths like sigma, delta etc.

There is a best software only for ALL math equations via Microsoft.
That is obviously “Microsoft Math”.

Test some screenshots:

http://img249.imageshack.us/img249/6329/ssinkl1aeb66amo3.jpg

http://2.bp.blogspot.com/_GHp2s2v3Mx4/TUBgPK2vRcI/AAAAAAAABsg/Y-Y3bqPGGf0/s1600/microsoft+math.gif

http://www.file-extensions.org/imgs/app-picture/5682/microsoft-math.png

You can choose Formula Publisher in MICROSOFT office 07 or select an amenable source softwares like LibreOffice http://www.libreoffice.org/.