Beginner Project: Chrome, Use Of Eval(), Detecting Window Size?

I have done some ugly hacking in JavaScript before but nothing serious. Now I have decided to learn the language properly, so yesterday I threw together a function plotter that you can see here: balazsbotond dot hu/plotterThe script is here: balazsbotond dot hu/plotter/raphael-test.jsI use Google Chrome as my primary browser. My script works perfectly in every other browser (IE6, IE8, FF, Opera, Safari), but there are some problems in Chrome. Some functions do not work at all (exp()), some do not always work (sin(x) works, x*sin(x) works sometimes, 0.7*x*sin(x) never works). Since I am new to JS and this seems to be a very subtle problem, I have no idea where to start.

I have read that the use of eval() is not recommended because of performance and security reasons. erformance is not a problem here (eval is definitely better here than writing my own expression parser), but what about security? Did my use of eval introduce a security risk in my site (I find this quite unlikely because the whole thing runs on the client side but who knows...)?By the way, is there a way to detect if eval() was not successful?And finally, is there a reliable, cross-browser way of getting the client size of the window? I'm talking about the size without the title bar, toolbars, etc. My solution does not work in IE6 and IE8.