How do I specify a set number of decimal places after the decimal? 

I've just created a very long document.  Without having to scour the entire document to see what expression I've assigned to a certain variable how can I recall my original expression after I've assigned values to the variables in it?

When I plot(cos(2*x^2)) the plot doesn't look right.  The graph area between -7 and -8 jumps and similarily on the positive x-axis.  It doesn't appear to affect values just the visualization of graphs.  If you plot(cos(2*x^2),x=-7..-8) the graph is fine. 

Can't seem to figure out how to change the background colour of a worksheet.

It's not a simple right click on the background as one would think as that option is not available.  And it's not in the tools option menu.  Can it be done?

plot (arccos(cos(x)),x);

At x=0, arccos(cos(x)) should be shown on the graph at (0,0),  As I zoom in I find that Maple draws it at closer to the point (.01,-.01) not at all at (0,0)