Spanton, J. Humphrey (John Humphrey) · London, Macmillan and Co., Limited; New York, The Macmillan Company · leaf 107
B. Trisect the angleDCB in E and F (Prob. 13). Trisect the angle ECB in H andK (Prob. 14). Bisect FKin L (Prob. 12). ThenDE = 3o°,EH = 2o°,HF=io°,and FL = 5°. Thereforebetween D and B we canconstruct any angle that is amultiple of 5°. Divide the angle ACD intofive equal parts by the radiifrom M, N,… … tig. 193. 94 GEOMETRICAL DRAWING AND DESIGN. If we subtract the multiples of 5° from those of 6° we canobtain any desired angle, e.g.— 6- 5 = 1° 12-10 = 2° 18-15 = 3°24-20 = 4° 30-25 = 5° etc. etc. etc. All the regular polygons, with the exception of two—theheptagon and undecagon—can be constructed…
Geometrical drawing · Design · Drawing
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