Given a straightedge with two parallel sides a given distance *d* apart, one can draw
a line parallel to a given line at a distance *d* from it and one can
draw parallel lines between any two points if the distance between the points
is greater than *d*. Using only such a straightedge, give a general procedure for
the following constructions.

- Bisect a given angle.
- Bisect a given segment.
- Construct a line parallel to a given line through a point not on the given line.
- Construct a line through a point that is perpendicular to a given line.

Which of the constructions above can be done if you are only allowed to use the
straightedge to draw a line parallel to a given line at a distance *d* from it?

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Source: Inspired by a problem proposed, but not used, for the IMO
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The solution will be posted shortly.
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