Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes and company · leaf 91
a of the parallelogram is equal to AB x BE. Cor. Parallelograms of equal bases are to each other as thenaltitudes ; and if their altitudes are equal, they are to eachother as their bases. For, let B be the common base, and C and D the altitudes01 two parallelograms. Then, by the theorem, theii… … Areas cf Triangles and Trapezoids. THEOREM IX The area of a triangle is equal to half &•,„ product of its base byits altitude. Let ABC be any triangle and CD itsaltitude : then will its area be equal tohalf the product of ABx CD. For, through B draw BE parallel toAC, and through C draw CE…
Geometry · Plane trigonometry
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