Problem of the Month

• Everyone is welcome to participate, but only undergraduate OU students are eligible for the prizes.
• If there is more than one correct submission, the evaluation committee will select a winner.
• A complete solution to the problem must include a proof.
• Solutions to the Problem of the Month can be submitted in the Math Department's office (PHSC 423).
• Make sure that your submission includes your name and OU email.
• The deadline for submission is the last day of the month.

Congratulations to Sawyer Robertson, winner of the November 2019 Problem of the Month competition!

Parallel lines

Given a square $$ABCD$$, we take points $$E$$ and $$F$$ in the interior of the segments $$BC$$ and $$CD$$, respectively, so that $$\angle EAF = 45^\circ$$. The straight lines $$AE$$ and $$AF$$ intersect the circumscribed circle of the square $$ABCD$$ at the points $$G$$ and $$H$$, respectively. Show that the lines $$EF$$ and $$GH$$ are parallel.