## Online Course Discussion Forum

### Math Challenge II-A Fall 2019

We got a question about problem 2.9: How to prove that $PQ = QP'$?

Here's a hint: The fact that $\triangle APQ$ has perimeter $2$ is crucial into proving that $PQ - QP'$. Try writing the length of segments in the diagram in terms of the lengths of the sides of $\triangle APQ$.

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