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MathNet 2021 — Part 08 Question 53

Math Olympiad Vault · MathNet 2021 — Part 08

Question 53

A parallelogram $ABCD$ has side lengths $|AB|=7\,\mathrm{cm}$ and $|BC|=5\,\mathrm{cm}$. Its altitude to $AB$ is $4\,\mathrm{cm}$, and $\alpha=\angle BAD$ is acute.

Part a. Construct the parallelogram with straightedge and compass, and draw the circumcircle of triangle $BCD$. Label the circumcenter $S$.

Part b. Round the larger of the two angles $\angle BSD$ (the reflex angle) to $254^\circ$ and use this value in subsequent calculations. Find the interior angles of the parallelogram.

Part c. Find the obtuse angle between the perpendicular bisector of $AD$ and the altitude to $AB$.