There is a square A 1 B 1 C 1 D 1 with one of its side lengths 7 .
For every natural number n < N , conduct these:
1. Let E n , F n be the midpoints of B n C n , C n D n respectively.
2. Let G n , B n + 1 be the intersections of A n E n , A n C n with B n F n .
3. Pick a point C n + 1 on C n D n such that A n C n is perpendicular to B n + 1 C n + 1 .
4. Pick a point D n + 1 on A n D n and A n + 1 on A n C n such that B n + 1 C n + 1 is perpendicular to C n + 1 D n + 1 and parallel to D n + 1 A n + 1 .
Find the area of the colored area as N approaches infinity.
This problem is a part of <Christmas Streak 2017> series .
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The areas of the triangles in the largest square are 2 0 4 9 , 1 5 9 8 , and 1 2 4 9 , which sum to 1 5 1 9 6 . The geometric progression of the areas of the squares has common ratio 9 2 , and so we calculate k = 0 ∑ ∞ ( ( 9 2 ) k × 1 5 1 9 6 ) = 5 8 4 = 1 6 . 8 .