geogebra breaks with redefinition error
1. Enter this curve:
c = curve[t cos(t),t sin(t),t,0,pi]
2. Define point on c and tangent line to the curve at that point:
A = Point[c]
3. Try to redefine the curve:
c = curve[r(t) cos(t),r(t) sin(t),t,0,pi]
Geogebra (version 3.2.16, win xp, java 1.6) will give a redefinition failed error, but it will not recover. The drawing pad is blank and tools do not work. You cannot undo.
You need to have the tangent line to get the error.