Question 17
$ABCD$ is a trapezoid with parallel bases $AB,CD$, where $AB<CD$. Point $M$ is the midpoint of $CD$, and $N$ is inside the trapezoid with $AN=BC$ and $BN=AD$. If $\angle AMB=90^\circ$, prove that quadrilaterals $ANMD$ and $BNMC$ have equal areas.
