# Intersecting lines & vertically opposite angles

- Author:
- Jill Alsman, Mathguru

- Topic:
- Straight Lines

You are given line segment AB with point E on it. You may move points A, B and E. The measure of angle DEB can be adjusted by moving the slider labeled α, and angle AEC can be adjusted by the β slider.
Move the points and the sliders around to see how they effect the image. Come up with some observations.
1. What affect does moving Points A or B have on the image?
2. What effect does point E have?
3. What happens when you move slider α?
4. What happens when you move slider β?
5. When α = β, what do you notice? What is formed?
6. Is your observation in #5 ALWAYS true?
7. What conclusion can be made based off your observation?