for intersecting lines,vertically opposite angles are equal

We can see a line segment AB in black color and a point E is in present on it. Line segment EC is drawn at an angle β with AE (in anti clock direction) and a line segment ED is drawn at an angle α with EB (in anti clock direction). We can change the values of α and β using their respective slide bars. We can also move the points A, B and E. Let us move these free points and change the values of the angles and see how the lines change.
Questions to think about 1. What do we observe when α=β?