I'm going to be a new physics major in the fall. I think a graphing calculator is almost a necessity, but how "hi-tech" do I need? The graphing calculators from TI range anywheres from $100-$150. Do I need to get top-of-the-line? I don't want to spend an extra $50 if I don't need to, but I don't want to spend $100 on a calculator and not have it be good enough either. Thanks!