Your code works for me, unchanged. Do you get an empty plot or nothing at all?

@Mörre Noseshine Apparently the constant N[A] uses the unit 'mole'. I don't know why that is. The system 'CGS' does not contain a unit for "amount of substance", which is the dimension whose standard unit is 'mole'. Using the AddSystem command to add 'mole' to the system 'CGS' in the way that I showed corrects the problem. Be happy for that.

The concepts of a Units environment and a Units system are othogonal. 'CGS' is not an alternative to Natural; rather, 'CGS' is an alternative to 'SI', which is the default system that is loaded for either environment Natural or environment Standard. Having a Units environment loaded tells Maple to automatically convert and cancel units upon entry. The Units system tells it what units to convert to. If I were writing it, then every system would have a unit for every fundamental dimension. Perhaps MapleSoft had a reason for not doing it that way, or perhaps it should be considered a bug.

@Mörre Noseshine I'll need to see the full code that led to the error with evalf(84000/Constant(N[A])). Are you trying to use the ScientificConstants package?

@Mörre Noseshine Wow, I guess they never added 'mole' to the 'CGS' system! Well, you'll have to add it yourself, like this:

restart:
with(Units:-Natural): #or with(Units:-Standard):
Units:-AddSystem('CGS', Units:-GetSystem('CGS'), 'mole');
Units:-UseSystem('CGS');

@rit What you have listed is the Hessian of f, which is the Jacobian of the gradient of f, as Acer said. The Hessian can be thought of as the second derivative of a function f:R^n -> R.

@lutfi Your "some weird reason" was probably that you did not include option allsolutions to solve.

@abscissa 

Yes. For example:

J1:= eval(J, [a= 1, b= 2, c= 3, d= 4, e= 5, f= 6, g= 7, h= 8, s= 9, t= 10, u= 11, v= 12]);

You may use the same command to provide numeric values for the parameters also.

@Mörre Noseshine On this site, you can vote up for Questions, Answers, and Posts, but there is no equivalent to StackExchange's ability to accept one Answer as the answer.

@Preben Alsholm Could you explain this more? What is the significance of t = 76.239? That appears to be the location of the rightmost local min of abs(y2-y3). Why doesn't b(t) record the local min at about t = 73 or the local maxes at about t = 74 and t = 78?

Why is the events criterion based the right sides of equations 2 and 3. Why not use the simpler left sides?

In other words, given a function x(t) on t = 0..1 and integers r >= 0 and N > 0, you want to find the (2*r+1)*N coefficient functions X[m,n](t), m= 0..2*r, n= 1..N, which in some sense minimize the error of the approximation

x(t) ~ sum(sum(X[n,m](t)*b[n,m](t), m= 0..2*r), n= 1..N)

where the b[n,m](t) are fixed basis functions given by

piecewise(n-1 <= N*t and N*t < n, piecewise(m <= r, cos(P*m*t), sin(P*(m-r)*t)))

with P = 2*Pi*N.

Note that I removed the treatment of m=0 as a special case because that's redundant.

@phil76600 You have a homogenous, linear, second-order differential equation with two initial conditions set to 0. The solution is thus the identically zero function. If you look closely at the x-axis of the plot, you'll see that the curve lies along it. Or you can set the plot option axes= boxed:

odeplot(sol, axes= boxed);

and then the curve y = 0 will be obvious.

If you want a different solution, then you need to use different initial conditions.

@janhardo I don't know what went wrong for you. You do have the correct path, because you would've received an error message if you did not. Just try the commands

showstat(AddFractions);

etc.

@Carl Love The .m file contains procedures named AddFractions, DrawFraction, FractionOptions, MultFractions, CompareFractions, and `convert/decimalfraction`. All of these are listable with showstat. I do not think that it has a procedure named mod, although I cannot tell you why mod shows up in the anames list.

@janhardo Send it to me by email. I'll send you an email that you can reply to.

Does OS X Mavericks use backslash as a directory name separator? I thought that only Windows used that. (Even Windows allows the forward slash instead.) Try replacing the double backslashes \\ with single forward slashes /.