In convex quadrilateral $ABCD$, $AB=BC=13$, $CD=DA=10$, and $\angle D=60^\circ$. Points $X$ and $Y$ are the midpoints of $\overline{BC}$ and $\overline{DA}$ respectively. Compute $XY^2$ (the square of the length of $XY$).
Here :
https://web2.0calc.com/questions/in-convex-quadrilateral-abcd-ab-bc-13-cd-da-24-and_1
+816 
