Question 9In triangle $ABC$, $AB=AC$, $\angle ABC=40^\circ$, and $D\in AC$ with $BD$ bisecting $\angle ABC$. Extend $BD$ beyond $D$ to $E$ with $DE=AD$. Find $\angle ECA$. $20^\circ$$30^\circ$$40^\circ$$45^\circ$$50^\circ$
