%piecewise(``, x+y-2*z = 1, ``, 2*x+y-3*z = 5, ``, -x+y+z = 1); What does % here do?

I can find no help page to explain the functionality of the percent sign in this command and removing it produces an error. Please explain this.

A procedure can be made available in many worksheets by copying its original commands to each such worksheet. Is there a better way to include and invoke such a procedure in multiple worksheets?

My 5 year old laptop executes some commands very slowly e.g. plottools(rotate) around a line which is not a Cartesian axis. I intend to buy a new desktop. Which off-the-shelf desktops provide the fastest processing of Maple commands which do not include large data sets? Which provide the best price/performance?

What Maple15 commands will display a Rouleaux tetrahedron or a Meissner tetrahedron?

In Maple15, in spherical coordinates, what statements plot covariant vector [1,r^2*sin(theta),sin^2(theta)] and its contravariant equivalent [1,sin(theta),1/r^2] within their respective bases vectors. Assume r = 2, theta = pi/6 and phi = pi/4. I presume each plot will display the same space vector.