Given two parallel lines m and n, let A and B be points on m, and let C and D be the feet of the perpendiculars from A and B to n, respectively.
1. Are the lines AC and BC parallel? How do we know this?
2. Is ABDC a parallelogram? How do we know this?
3. What are the angles of ABCD at C and D? How do we know this?
Given the conclusions above, what does this say about the distance from m to n?