I've had good success with wxMaxima as well, but none of the equations I've worked with can fill a blackboard. SymPy is very nice as well, but for obvious reasons, it feels a bit more forced when interacting with it.

Do you accept the output from Climaxima? Granted, the project isn't near finished (currently held back due to some dependency issues).

I included some example videos in this reply: https://news.ycombinator.com/item?id=24467593

I use Sympy interactively, and I don't know what you mean by "forced". It doesn't feel that way to me.

this is a bit rush, but an example setting up the quadratic equation.

  f(x) := a*x^2 + b*x + c
  solve( f(x),x );
  
  from sympy import symbols, solve
  a, b, c, x = sympy.symbols(('a', 'b', 'c', 'x'))
  y = sympy.Eq(a*x**2+b*x+c, 0)
  solve(y, x)

I would change the first two lines to:

  from sympy.abc import *
  from sympy import *

I would put that into a file, and auto-load it at startup so I don't need to run it manually every time - one way of doing that is using iPython profiles.

Also put this in your startup file to get more pleasant looking output:

  init_printing(use_unicode=True)

Once you've done that, you only need to type:

  y = a*x**2 + b*x + c
  solve(y,x)

SymPy already comes with `isympy` script that will import everything from SymPy and create some common symbols (x, y, z, t, k, m, n, f, g, h) using either `python` or `ipython` (default). To do what you said the following script may be run.

  #!/usr/bin/env python
  from sympy.abc import *
  from sympy import *
  import code
  init_printing()
  code.interact(local=locals())