PhyTch.Paul

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13 years, 205 days

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These are questions asked by PhyTch.Paul

I have been messing with the various functions in the VectorCalculus package and have been getting some unexpected behavior w.r.t. some of the functions. My current issue is with the SurfaceInt function. Consider a sphere whose surface density increases linearly from one point on the sphere to the opposite pole. What is its overall mass. I set up the package... > restart; > with(VectorCalculus); > SetCoordinates(spherical[r, phi, theta]); and a density function... rho := proc (r, phi, theta) options operator, arrow; phi end proc; and perform the integration...
I know I haven't figured out all the limitations of Maple yet to avoid all the "gotcha"s but this should be straightforward, right? with (VectorCalculus): b(x,y,z) := VectorField(
I am trying to use the subs command to take a general solution to a differential equation and apply some numerical values. I can't seem to get the system to recognize the values I am substituting for. Consider the following: m*diff(y(t),t,t)=-m*g+sigma*A*diff(y(t),t); (1) y(0)=h,D(y)(0)=0; (2) dsolve( {(1),(2)} ); (3) subs( {A=2,m=50},rhs((3)) ); Everything works fine. If, on the other hand I impose any kind of constraint on A or m in the original equation then the substitution fails (nothing happens). Clearly the system has tagged the value for A and m as something other than their original name. Since the system doesn't report this name change how can I make substitutions after a symbolic manipulation like this?
I wish to set the default location for the "backup files" so they don't clutter my $HOME directory. It seems to me that this should be an easy thing to do but I can't find any reference in any of the documentation sources. Everytime I use Maple and quit my home directory is littered with as many as 45 small files which (I presume) are intermediate save files from a session. I don't mind having the program autosave but can I assign this location to some special scratch folder? OS: Mac OS 10.4, G5, Maple 10.
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