Kenison, Ervin, Bradley, Harry Cyrus, 1871-1936 · New York : The Macmillan Company · leaf 77
th //. Similarly, in Fig. Kll. we found, ;is an incidental part of theconstruction, the angle (3 which the line ab makes with 1. 56 DESCRIPTIVE GEOMETRY [VIII, § 80 80. Second Method for Finding True Length. The true lengthof a straight line may also be found by revolving the line aboutone of its… … Fig. 102. Analysis (Fig. 102). Let ab be the given line, projected onany plane Q at aqbq. Revolve the plane abbqa? about aqbq asaxis into Q. Then a falls at ar, where ara equals aa, and isperpendicular to aqb (§ 76); b falls at br, with brbq equal tobbq and perpendicular to aqbq; hence arbr equals…
Geometry, Descriptive
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