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murshid_islam
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- Question about a proof from Euclid's "Elements" Redux (by Daniel Callahan and John Casey)
The following proof (in the image below) is from the book Euclid's "Elements" Redux (by Daniel Callahan and John Casey). I did not understand why the point D or the ##\triangle \rm ABD## was necessary. (I mean, what was the "point" of D? ) Joking apart, wasn't this sufficient: suppose we have a line segment AB and a point C on AB such that AB=2AC. Let AC = x. Then AB = 2x. Therefore, AB2 = (2x)2 = 4(x)2 = 4(AC)2
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