Question 5
In the figure below, $ABC$ is an isosceles triangle inscribed in a circle with centre $O$ and diameter $AD$, with $AB=AC$. $AD$ intersects $BC$ at $E$, and $F$ is the midpoint of $OE$. Given that $BD$ is parallel to $FC$ and $BC=2\sqrt5$ cm, find the length of $CD$ in cm.
