GeometryDifficulty 4.6AIMEFind the answerUnited States
Problem:
Square ABCD is drawn. Isosceles triangle CDE is drawn with E a right angle. Square DEFG is drawn. Isosceles triangle FGH is drawn with H a right angle. This process is repeated infinitely so that no two figures overlap each other. If square ABCD has area 1, compute the area of the entire figure.
A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.
Solution
Solution:
Let the area of the nth square drawn be Sn and the area of the nth triangle be Tn. Since the hypotenuse of the nth triangle is of length Sn, its legs are of length l=2Sn, so Sn+1=l2=2Sn and Tn=2l2=4Sn. Using the recursion relations, Sn=2n−11 and Tn=2n+11, so Sn+Tn=2n−11+2n+11=(21+2)2n1=252n1. Thus the total area of the figure is ∑n=1∞Sn+Tn=25∑n=1∞2n1=25.
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Source: MathNet,
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