The American house-carpenter; a treatise on the art of building, and the strength of materials (1867)
Hatfield, R. G. (Robert Griffith), 1815-1879 · New York, J. Wiley · leaf 76
e parallels, the parallelo-gram will be equal to double the triangle. Thus, the paral-lelogram, a d, {Fig. 103,) is double, {Art. 143,) the triangle,c e d. 147.—Proposition. Let abed, {Fig. 104,) be a given quad-rangle with the diagonal, a d. From b, draw b e,parallel toa d;extend cdto e ; join a… … lels, a d and h e, they are therefore equal, [Art. 145, 146 ;) andsince the triangle, C, is common to both, the remaining triangles, Aand -B, are therefore equal; then B being equal to A^ the triangle,a e c, is equal to the quadrangle, abed. »
Carpentry · Architecture
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