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
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. » … 148.—Proposition. If two straight lines cut each other, asa h and c c?, [Fig. 105,) the vertical, or opposite angles, A andC, are equal. Thus, a e, standing upon c c?, forms the angles,B and O, which together amount, [Art. 137,) to two right angles;in the same manner, the angles, A and 5, form two…
Carpentry · Architecture
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