MathNet 2019-part-07 — 184 problems (EN–VI) Question 1

Let $ABC$ be a triangle with $\angle CAB = 2 \cdot \angle ABC$. Assume that there is a point $D$ in the interior of triangle $ABC$ such that $AD = BD$ and $CD = AC$. Show that $\angle ACB = 3 \cdot \angle DCB$.