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Source: BdMO 2024 Secondary National P7 Higher Secondary National P2

March 18, 2024
geometryperpendicular linescartesian coordinates

Problem Statement

Let ABCDABCD be a square. EE and FF lie on sides ABAB and BCBC, respectively, such that BE=BFBE = BF. The line perpendicular to CECE, which passes through BB, intersects CECE and ADAD at points GG and HH, respectively. The lines FHFH and CECE intersect at point PP and the lines GFGF and CDCD intersect at point QQ. Prove that the line DPDP is perpendicular to the line BQBQ.