Complex Calculation made easy at easycalculation

[jebem]

You mean this site?
Nice one. It all depends on what are your needs after all.

You may like to have a look to wolframalpha here as well.
It is not for free, but this is probably one of the top sites for symbolic algebra and you can take advantage of it for free as long as you don't exaggerate on the time spent in the site.

Also you may like to download and install XCAS (used in a more simplified version in the HP-PRIME calculators).