MathNet 2019-part-05 — 184 problems (EN–VI) Question 77

Let $ABCD$ be a square and $E$ an arbitrary point on the side $(CD)$. On the outside of the triangle $ABE$ one considers the squares $ENMA$ and $EBQP$. Prove that:

a) $ND = PC$;

b) $ND \perp PC$.