Question 19
Let $ABC$ be an acute, non-isosceles triangle. Take two points $D, E$ inside this triangle such that
$$
\begin{aligned}
& \angle DAB = \angle DCB, \quad \angle DAC = \angle DBC; \\
& \angle EAB = \angle EBC, \quad \angle EAC = \angle ECB.
\end{aligned}
$$
Prove that triangle $ADE$ is right.
$$
\begin{aligned}
& \angle DAB = \angle DCB, \quad \angle DAC = \angle DBC; \\
& \angle EAB = \angle EBC, \quad \angle EAC = \angle ECB.
\end{aligned}
$$
Prove that triangle $ADE$ is right.