Algebra is a proof-of-concept computer algebra system that displays each step in formula simplification, and can understand different input syntaxes. I wrote it in Christmas 2005 for the first Extend Firefox contest.
The functions actually evaluated are:
+-*/), powers (
a**bin some input syntaxes), square roots (
sqrt), n-th roots (
root), basic trigonometric functions (
tan), integer and floating point numbers, and the numeric symbols
It shares some code with Sentido, and I plan to combine them eventually. For now it is available here: algebra.xpi, just updated to work in Firefox 10. To start it pick the "Algebra" option in the "Tools" menu, or press Control+Alt+A, or in Apple computers ⌘+Alt+A.