Maths graphical tools

[rela]

Dear all valuable experts,

I'm looking for a free based maths graph plotting software which could display a sketch for various or any kind of functions supplied.

Any idea if such software even exists?

Thanks in advance.

[nicktacik]

I use this one
http://www.zdnet.com.au/downloads/0,139024478,10278409s,00.htm

[neutrino]

www.gnuplot.info

[rela]

Thank you so much guys.