Higbee, F. G · New York, John Wiley & Sons · leaf 100
SURFACES 89 on a plane surface so that all the elements will coincide with theplane. In Fig. 73 is shown a cone lying in a plane so that theelement OX coincides with plane. If the cone be now rolledout the curve of the base will rectify itself on the line xx as theelements of the surface… … Fig. 73. these obviously are the only surfaces whose elements may bemade to lie in a plane without changing their relation to eachother. In practice, however, a number of warped and doublecurved surfaces are considered developable; this is made possibleby approximate methods of development which…
Geometry, Descriptive
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