Young, George, jr, Baxter, Hubert Eugene, joint author · New York, Macmillan · leaf 48
The proof is as follows.(See Fig. 26.) Let ab> beany line. The angles 1 and2 are the angles which thegiven line makes with H andVrespectively. To prove that1 + 2 cannot exceed 90°. Inthe right triangle acib, theside att* < ob. The righttriangles aa/tf and abl^have a common hj^jotenuse;hence… … FiQ. 26 base. Thus 2 < 3. But, 1 + 3 = 90°parallel to P, ab coincides with ac^. 30 DESCRIPTIVE GEOMETRY [III, § 27 27. Second Method for Finding True Length. The secondmethod, as well as the first, depends on having the line parallelto a plane of projection. It diflfers from the first method,…
Geometry, Descriptive
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