I am interest in some type of mathematical solfwares. I heard mathematia is good, but i just think it is too expensive. I think it cost 1800 dollars for mathematica professionals, and 138 dollars for mathematia for students. Are there ways to get mathematica cheaper? If i do buy mathematica for student; how much to upgrade it to professional after i graduate? Are there cheaper math solfwares? perhaps some math freeware?