Elements of plane and solid free-hand geometrical drawing, with lettering; and some elements of geometrical ornamental design, including the principals of harmonic angular ratios, etc. In three parts ... for draughtsmen and artisans; and teachers and students of industrial and mechanical drawing (1878)
Warren, S. Edward (Samuel Edward), 1831-1909 · New York, J. Wiley & sons · leaf 148
arch tosupply it, devised the egg-curve which he called the compositeellipse, Fig. 21. Here, the points A, B, C, are foci, and D isthe describing point. That is, pins being set at A, B, C, Dand an inelastic string tied tightly around the four, the pin atD is then replaced by a moving pencil point,… … arcs; first mJ)n, with B and C for its foci; second no, withA and B for foci; third, op, with A and C for foci; next, theshort arc pq with B and C again as foci, etc. The curves thusformed are divided by Hay into five classes, according asthe angle at D is 90°, 108°, 120°, 135°, 144°, these all…
Geometrical drawing · Mechanical drawing
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