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MathNet 1984 — Part 01 Question 1

Math Olympiad Vault · MathNet 1984 — Part 01

Question 1

Given a regular dodecahedron of side $a$. Take two pairs of opposite faces: $E, E'$ and $F, F'$. For the pair $E, E'$ take the line joining the centers of the faces and take points $A$ and $C$ on the line each a distance $m$ outside one of the faces. Similarly, take $B$ and $D$ on the line joining the centers of $F, F'$ each a distance $m$ outside one of the faces. Show that $ABCD$ is a rectangle and find the ratio of its side lengths.