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 39
Ex. 70. Divide a right angle into two parts, one of 40° theother of 50°. This can be most easily done by finding one-thirdof the right angle, and making the angle and arc of 40°, one-thirdgreater than the one of 30°, thus : … Ex. 71. Repeat the divisions of the right angle, given in the 26 FREE-HAND GEOMETRICAL DRAWING. preceding examples, upon right angles in various oblique positions as in Ex, 36. Practical Examples.
Geometrical drawing · Mechanical drawing
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