Algebra is a computer algebra system that displays each step in formula simplification, and can understand many different syntaxes.

I wrote it in Christmas 2005 for the first Extend Firefox contest, but the version submitted, just a couple of minutes before closing, had a few problems:

• To evaluate an expression, you have to press [shift]+[return], no matter what interface style you choose. This should vary with the style, as with some it should be possible to just press [return] at the end of the line after you put a semicolon ";" there, but then the parser will not work and the expression will be left unevaluated. The easiest way to work around it is to select the "Mma" style (which uses no semicolons) and use [shift]+[return] or [enter] (numeric keypad). (fixed afterwards)
• The functions actually evaluated are:
  • automatic simplification of addition and subtraction of integers.
  • plotting of functions including arithmetic operators (+-*/), powers (a^b, or a**b in some styles), square roots (sqrt), n-th roots (root), basic trigonometric functions (sin, cos, tan), integer and floating point numbers, and the numeric symbols π and ⅇ. (in the current version, plots are exported to SVG and Postscript.)
• The menu entry in "Help > About" does not work, because the "about.xul" file is not even well-formed XML. (fixed afterwards)

It shares some code with Sentido, and I plan to combine them eventually.