Mathomatic is a portable Computer Algebra System (CAS) that can solve,
simplify, and compare algebraic equations, perform standard, complex number, modular, and polynomial arithmetic, etc. It does some calculus and is very easy to compile, learn, and use. Plotting functions with gnuplot is also supported.
Tips to Use
Mathomatic is best run from within a terminal emulator. First you type in your algebraic equations in standard infix notation, then you can solve them by typing in the variable name at the prompt, or perform operations on them with simple English commands. Type "help" or "?" for the help command. If the command is longer than 4 letters, you only need to type in the first 4 letters. Most commands operate on the current equation by default.