A Manual of Elementary Geometrical Drawing, Involving Three Dimensions: Designed for Use in High Schools, Academies, Engineering Schools, Etc.: and for the Self-instruction of Inventors, Artizans, Etc. ... In Five Divisions ...

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J. Wiley and son, 1867 - Geometrical drawing - 121 pages
 

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Page 2 - See cd — c'd', the projections of cd, PI. I., Fig. 2. 9. Remark. A general principle, which it is important to be perfectly familiar with, is embodied in several of the preceding examples; viz. When any line is parallel to either plane of projection, its projection on that plane is equal and parallel to itself, and its projection on the other plane is parallel to the ground line. 10. The preceding remark serves to show how to find the true length of a line, when its projections are given. When...
Page 2 - ... is oblique to both planes of projection, its length, V<7, is evidently equal to the hypothenuse of a right-angled triangle, of which the base is vg, the horizontal projection of the line, and the altitude is Vw, the height of the upper extremity, V, above the horizontal plane.
Page 26 - and d' are found. Second. To find other intermediate points. Take the two points whose horizontal projection is G, for example. They are on the horizontal elements, one on the upper, and the other on the lower half of the horizontal cylinder, and whose horizontal projection is ST.
Page 1 - MR, of a horizontal, and a vertical plane of projection,is the ground line for that vertical plane. 6. The preceding definitions enable us to express a fourth fundamental principle more briefly than could otherwise be done; viz., The height of the vertical projection of a point above the ground line, is equal to the height of the point itself, in space, above the horizontal plane ; and the perpendicular distance of the horizontal projection of a point from the ground line, is equal to the perpendicular...
Page 2 - PI. I., Fig. 1, does not touch either plane of projection, it is evidently equal to the hypothenuse of a right-angled triangle, of which the base, CH, equals the horizontal projection, ad, and the altitude...

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