Find area under curve :
please check out [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=806.0]Integrator y= ? f(x) dx[/url]

you can type in function y=f(x)

If you want to draw curve with parameters,
please check out [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=407.0]General purpose Curve plotting applets[/url] or [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=388.0]function plot[/url]