作業十一

11-1	Construct the portion of the cylinder x2 + y2 = 1 lying between the planes z = 0 and z = 1 + x.
11-2	Describe how two pipes of the same size are joined perpendicularly.
11-3	Construct two pipes joined as thus:
11-4	Describe how three pipes are symmetrically joined.
11-5	Wrap the graph of y = cos 2x around a cylinder.
11-6	Wrap the graph of y = cos 3x around a cylinder.
11-7	Construct the graph of z = x2 - y2 above the unit circle.
11-8	Construct the monkey's saddle given by z = x3 - 3xy2 above the unit circle.
11-9	Construct this model:
11-10	Construct this model:
11-11	Describe how 8 identical pipes are joined together symmetrically.