MathNet 2023-part-02 — 191 problems (EN–VI) Question 21

Let $ABC$ be a triangle and $O$ the centre of its circumcircle. Suppose that $\widehat{CBA}=60^{\circ}$ and $\widehat{CBO}=45^{\circ}$. Let $D$ be the intersection point of the lines $(AC)$ and $(BO)$. Show that $AD=DO$.