Hatfield, Robert Griffith, 1815-1879. [from old catalog] · New York & London, Wiley and Putnam · leaf 73
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 b 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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