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Ireland geometry
Problem
Let be a square. The line segment is divided internally at so that . Let be the midpoint of and be the midpoint of . Let be the point on such that is perpendicular to . Prove that .

Solution
Let have side length and write . Then, by assumption Because , Pythagoras gives .
Observe that and are similar. Hence, and so This implies .
Observe that and are similar. Hence, and so This implies .
Techniques
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