Given a square piece of paper of unit side length, you fold it such that one corner touches the opposite diagonal as illustrated by the above figure. If the folded segment is a triangle, what is its maximum possible area?
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Clearly, the maximum area is obtained when point F is at corner B , and in this case the fold line is the angle bisector of ∠ A B D .
Hence, A E = ( 1 ) tan 2 2 . 5 ∘ , and the maximum area = 2 1 tan 2 2 . 5 ∘ ≈ 0 . 2 0 7 1