Name your plots and use display. 

For example

restart;
with(plots):
a:=plot3d(sin(x*y),x=-Pi..Pi,y=-Pi..Pi):
b:=implicitplot3d({z-.5},x=-2..2,y=-2..2,z=-2..2,axes=box):
display({a,b});

This link will be of some help for you.  http://euler.slu.edu/GrantWebPages/PREP06Calc3Maple/pdfs/TripleIntegrals.pdf 

This may help

edit " deleted"  oops sorry I didn't see an above link going there already. 

A template for two variables

solve({eq1,eq2},{variable1,variable2});

Explain why Maple wouldn't be very useful with CFD?  Here's an interesting page which I happened to find  http://solidmechanics.org/FEA.htm 

The Cosmos Floworks analysis package in Solidworks, is a graphical user interface which uses the equations behind the scenes.  I suppose now I can see why you see Maple as currently not being very useful in such matters, it's not as easy to manipulate objects without first defining their boundaries in the form of an equation.

Thanks.  So in my previous post, something like this

Try looking in the help under CDF http://www.maplesoft.com/support/help/Maple/view.aspx?path=Statistics/CumulativeDistributionFunction but that doesn't really help you find the normal cumulative distribution.  You need to calculate it. 

That help can be found here  http://www.mas.ncl.ac.uk/~ndjw1/teaching/maple/ - Basic probability distributions with maple.  About 3/4 the way down the page you will see an example.

Does everyone else get nice smooth lines? 

I've tried increasing the grid[500,500] and numpoints=1000 but still can not get smooth lines. 

Is this a problem that maple has with contourplot???

Actually I've tried increasing the numpoints and grid.  The plot just isn't smooth between x and y at 0.3 to -0.3 

By curves I mean equipotential lines.

randomize();
rand();

otta do it. 

Seriously though no one can help you without you giving us more information.

Yes that is what I initially wanted.  Now how would get that curve?

Yes that helps.  Specifically I had

q:=2*10^(-7)*8.99*10^9;
v:=q/sqrt((x-a)^2+(y-b)^2);
 

g:=-diff(v,x);

charges:=subs(a=-1/2,b=0,v)+subs(a=1/2,b=0,v)-subs(a=0,b=3/4,v);

plot3d(charges,x=-2..2,y=-2..2,view=-2e4..2e4);

xg:=-diff(charges,x);
yg:=-diff(charges,y);

So the points where the field is zero is found here.
fsolve({xg=0,yg=0},{x,y},{x=-1..1},{y=-1..0});
fsolve({xg=0,yg=0},{x,y},{x=-1..1},{y=0..4});
 

Interesting problem.  My probability skills are a bit rusty but a thought came up. 

The student's seat where the drunken student is sitting will help the drunk to his proper seat.  So the probability would be 100% that the last student will sit in his own seat.

So with that command I'd need to explicitly tell maple to draw a line with point (1,2,z). 

What I have is a 3d plot from the plot3d command of the electric potential for 3 charges and I want to plot the line where the electric field is zero.  So in this case would I assign a value to a variable for plot3d and another variable for the line and use the display command to show both of them on the same graph?