Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 144
zontalplane, every point in it, as A, in as-suming its new position, simply movesin a horizontal plane, and will there-fore be at the same distance above theground line that it was in the eleva-tion (Fig. 260), and it will also be inthe perpendicular A A; the point ofintersection A is, therefore,… … Fig. 261, CONIC SECTIONS. The plan of the cone (Fig. 262) is simply a circle, described from the centreS, with a diameter equal to that of the base. Its elevation is an isoscelestriangle, obtained by drawing tangents A A, BB, perpendicular to andintersecting the ground line; then set off upon the…
Mechanical drawing
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