MathDB
concurent wanted, _|_ diagonals in convex quadr. 1991 Kyiv City MO 8.5

Source:

July 19, 2021
geometryconcurrencyconcurrent

Problem Statement

The diagonals of the convex quadrilateral ABCDABCD are mutually perpendicular. Through the midpoint of the sides ABAB and ADAD draw lines, which are perpendicular to the opposite sides. Prove that they intersect on line ACAC.