The Undo command undoes the rule most recently applied to the problem expr.  It returns the previous state of the problem. This operation can be repeated until the problem is in its initial state.

Maple commands other than the package commands Rule and Hint do not change the Calculus1 internal state of a problem. Therefore, Undo does not undo the results of applying such commands.  However, you can usually recover the prior state of such a problem by calling GetProblem.

The normal input to Undo is the output from a previous call to Rule or GetProblem. To pass the output of GetProblem to Undo, use the internal option to GetProblem. However, the routine tries to match any expr to an existing problem.

This command can be used within a tutor after applying a Rule interactively by using the DiffTutor, IntTutor, or LimitTutor.

$\mathrm{with}\left(\mathrm{Student}\left[\mathrm{Calculus1}\right]\right)\:$

$\mathrm{infolevel}\left[\mathrm{Student}\left[\mathrm{Calculus1}\right]\right]≔1\:$

$\mathrm{Rule}\left[\mathrm{change},u=2x\right]\left(\mathrm{Int}\left(\sin \left(3x\right)\,x\right)\right)$

Creating problem #1

Applying substitution x = 1/2*u, u = 2*x with dx = 1/2*du, du = 2*dx

$\int \sin \left(3x\right)\ⅆx=\int \frac{\sin \left(\frac{3u}{2}\right)}{2}\ⅆu$

$\mathrm{Undo}\left(\right)$

$\int \sin \left(3x\right)\ⅆx$

$\mathrm{Rule}\left[\mathrm{change},u=3x\right]\left(\right)$

Applying substitution x = 1/3*u, u = 3*x with dx = 1/3*du, du = 3*dx

$\int \sin \left(3x\right)\ⅆx=\int \frac{\sin \left(u\right)}{3}\ⅆu$

$\mathrm{Undo}\left(\right)$

$\int \sin \left(3x\right)\ⅆx$

$\mathrm{Undo}\left(\right)$

Error, (in Student:-Calculus1:-Undo) there is no previous state for this problem