# 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!

### February 2020

## 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.