13) In the adjacent figure, calculate $CD$ knowing that $OB=1$, $A \widehat{B} C=45^{\circ}, B \widehat{C} D=15^{\circ}$.

![](https://cdn.mathpix.com/cropped/2024_04_17_4c97eba1baa5e71bd15fg-2.jpg?height=351&width=328&top_left_y=414&top_left_x=1104)