pliable bands which can be joined together so as to make a circle witha diameter of eight inches. If these two semi-circumferences arestraightened out two comb-like forms are secured, and by inserting theteeth of one set between the teeth of the other set and closing the two to-gether a rectangle… … Fig. 1. Fig. 2. Fig. 1 and 2 demonstrate mechanically that the area of a triangle is equalto its base, multiplied by one-half its altitude. Fig. 1 illustrates the prob-lems when a perpendicular from the apex falls within the base, and Fig. 2when it falls outside the base. Both triangles are formed…
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