Compare the steps for constructing a perpendicular line to line AB through point using a reflective device and using paper. .
When using paper to construct the perpendicular line, the paper is folded so that
and the two sides of
line AB will lie exactly on top of each other.
When using a reflective device to construct a line perpendicular to line AB, set one end of the device to coincide with
and
then swing the other end of the device so the reflection of line AB coincides with