Explore! Parallel Lines Intersected by a Transversal
Only spend about 30 seconds here!
Lines a and b are parallel. They are cut by transversal c. Drag the blue points on c to move the transversal.
Think:
How does this affect the angles?
Which angles are always congruent?
Which angles are always supplementary?
Note: Do not allow the blue points to fall inside the parallel lines or the angles will disappear!