TITLE: A good, free, graphics package for mathematics?
QUESTION [8 upvotes]: A student of mine has cooked up a new graphical notation for computing with knots on surfaces. The trouble is, writing up his results is difficult due to his new notation. Is there a good "drawing tool" for mathematics that anyone can suggest?

REPLY [2 votes]: GeoGebra is nice tool that worth. I recomend using it.