# parallel lines and transversal

- Author:
- Mathguru

- Topic:
- Straight Lines

We can clearly see three lines. Two are blue and one is gray. We can change the position of these three lines with free points A, B, C, D and E. We can see that the gray line (transversal) intersects the two straight parallel lines (blue) and makes interior angles b, d, e and h and exterior angles a, c, f and g. In this situation 4 types of angles are formed.
1. Corresponding angles
2. Alternate interior angles
3. Alternate exterior angles
4. Interior angles on the same side of the transversal
c and e, a and h, d and f and b and g are pairs of corresponding angles. d and h and b and e are alternate interior angles. c and g and a and f are alternate exterior angles. b and h and d and e are interior angles on the same side of the transversal. Move the free objects A, B, C, D and E and observe how the angles get changed.

Questions to think about
1. What is the relation between c and e, a and h, d and f and b and g (that is, between the pairs of corresponding angles)?
2. What is the relation between d and h and b and e (that is, alternate interior angles)?
3. What is the relation between c and g and a and f (that is, alternate exterior angles)?
4. What is the relation between b and h and d and e (that is, interior angles on the same side of the transversal)?