Kenison, Ervin, Bradley, Harry Cyrus, 1871-1936 · New York : The Macmillan Company · leaf 114
andF-traces of such a plane. Suchcases may be tested by the useof the profile projection. Thus, inFig. 157, the line ab is found tobe perpendicular to the plane Q. 113. Perpendicular Planes. Iftwo planes are mutually perpen-dicular, the fact is not, in general,evident from the traces of theplanes.…
Geometry, Descriptive
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