When using paper to construct the perpendicular line, the paper is folded so that
and the two sides of line
will lie exactly on top of each other.

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

When using a reflective device to construct a line perpendicular to line
, set one end of the device to coincide with
, and then swing the other end of the device so the reflection of line
coincides with