It's one way to try, but not necessarily a good way. Suppose what you actually want to know is whether the determinant is 0 (which is pretty typical). That's a well-defined question for a square matrix with exact entries, but it becomes problematic for floats. The determinant is a polynomial in the entries of the matrix: if you're very lucky, converting the entries to rationals may hit on a point where that polynomial is exactly 0. More likely, it won't be exactly 0, even if the result "should" be 0 (i.e. the matrix is a floating-point approximation of a matrix whose determinant is 0). It may not even be small, if there are several large eigenvalues. A more stable way to tell would be to use the singular-value decomposition.

This is true, but simplify(..., size) should not give you that error message. It's a bug.

This is true, but simplify(..., size) should not give you that error message. It's a bug.

You're probably looking in the wrong place for them. They should be in the current directory, as returned by currentdir(). By default that is Maple's own directory, something like "C:\Program Files\Maple 11" if you're in Windows. You can change that, either by explicitly putting a path in the plotsetup command or with something like

> currentdir("C:\\MyFavouriteDirectory"):

(note the doubled backslash).

You're probably looking in the wrong place for them. They should be in the current directory, as returned by currentdir(). By default that is Maple's own directory, something like "C:\Program Files\Maple 11" if you're in Windows. You can change that, either by explicitly putting a path in the plotsetup command or with something like

> currentdir("C:\\MyFavouriteDirectory"):

(note the doubled backslash).

Because I pasted the wrong text: it should have been iquo(tens[m], sevens[m]) instead of floor(tens[m]/sevens[m]). I corrected it now.

Because I pasted the wrong text: it should have been iquo(tens[m], sevens[m]) instead of floor(tens[m]/sevens[m]). I corrected it now.

The basic difficulty is that for most tasks, the steps Maple uses are not at all the same as the ones people use in doing it by hand. The algorithms are likely to be completely different. A high-school student who wants to learn how to factor polynomials doesn't want to be told about the Cantor-Zassenhaus algorithm. So there can be no generalized option to "show the steps" in an arbitrary command: each Tutor must be programmed separately, and usually without reference to what Maple would use on its own for the same problem.

The basic difficulty is that for most tasks, the steps Maple uses are not at all the same as the ones people use in doing it by hand. The algorithms are likely to be completely different. A high-school student who wants to learn how to factor polynomials doesn't want to be told about the Cantor-Zassenhaus algorithm. So there can be no generalized option to "show the steps" in an arbitrary command: each Tutor must be programmed separately, and usually without reference to what Maple would use on its own for the same problem.

Many of us academics have some very bright, but not necessarily honest, students, and often must look at files created by them. For me that's the main source of worry about security in Maple. Given the motivation, it wouldn't be too far-fetched to imagine one of them learning how to create and hide code that might do damage to my system: perhaps to search for and destroy or alter files containing their grades in my course, if they're unsatisfied with what they got on a midterm. Using the -z option when looking at documents from students should make this difficult for them; I don't know how complete is the protection it provides.

When will I learn to always preview before posting? I fixed it now.

When will I learn to always preview before posting? I fixed it now.

It may help sometimes, but it is often misleading. evalb (A = B) returns true only when A and B are literally the same (after evaluation). It does not check for mathematical or logical equivalence. So for example,

> evalb((not(P and not Q)) = ((not P) or Q));

false

It may help sometimes, but it is often misleading. evalb (A = B) returns true only when A and B are literally the same (after evaluation). It does not check for mathematical or logical equivalence. So for example,

> evalb((not(P and not Q)) = ((not P) or Q));

false

Your loop variable is "date", but some of your code seems to assume that the loop variable is i. You never assigned values to i. I already told you this in my last comment.