Kenison, Ervin, Bradley, Harry Cyrus, 1871-1936 · New York : The Macmillan Company · leaf 166
llel to the same coordinate plane. Construction (Fig. 225). Let A and B be the given lines.Choose one of them, as A, for the axis. Since A is parallel toH, B must now be revolved about A until B, also, is parallel toH. Assume any point c(ch, cv) in the line B, at a reasonabledistance from the… … Fig. 225. this perpendicular, giving cr. Then ohcr is B revolved, Br,and the angle between Br and Ah is the true angle 8, betweenthe given lines. Proof of the Construction. Since Ais parallel to H, the revolution ofpoint c about A will project on H as astraight line perpendicular to Ah (§ 76).Hence…
Geometry, Descriptive
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