This is one of 10 modules from the published CD-ROM,
Introduction to 3D Spatial Visualization: An Active Approach
by Anne Frances Wysocki (software) and Sheryl Sorby (workbook),
based on work by Beverly Baartmans and Sheryl Sorby.
(Clifton Park, NY: Thomson-Delmar Learning, 2003)

If you cannot see an animated screen above, that is because
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