Haswell's engineers' and mechanics' pocket-book .. (1844)
Haswell, Chas. H. (Charles Haynes), 1809-1907 · New York, Harper & brothers · leaf 68
To find the Area of a Trapezoid—fig. 9. Rule.—Multiply the sura of the parallel sides a h, d c, by a h, theperpendicular distance between them, and half the product will bethe area. OF REGULAR POLYGONS. Rule.—Multiply half the perimeter of the figure by the perpen-dicular, falling from its centre…
Engineering · Mechanical engineering
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