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 62
In the first of these figures, the acute half angles are 20° and30°, whose ratio is therefore f. In the second figure the cor-responding angles are 18° and 36°, having therefore a ratio ofJ, and affording a more decidedly egg-shaped curve. Ex. 108. An egg-shaped oval may also be inscribed in…
Geometrical drawing · Mechanical drawing
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