In compass-and-straight-edge construction problems, we are allowed to make the following legal moves:
1) We can connect two points with a straight line.
2) We can find the point(s) of intersection of any two straight lines, a line and a circle, or two circles.
3) We can transfer lengths with the compass.
4) We can extend an existing line to arbitrary length.
5) We can construct a circle with a given center and radius.
Note that by a straight-edge, we do not mean a ruler - that is, a straight-edge cannot be used to measure arbitrary lengths. It is merely a straight line, with no quantitative or metric properties associated to it.
Using the aforementioned rules, a compass (if you don't have one handy, a pencil tied to a piece of string works just fine) and a straight-edge (a ruler, the edge of a book...):
a) (Easy) Duplicate an arbitrary angle.
b) (Easy) Bisect an arbitrary angle.
c) (Easy) Construct the perpendicular to a given line through a given point on the line.
d) (Medium) Construct the perpendicular to a given line through a given point off the line.
e) (Medium) Construct the parallel to a given line through a given point off the line.
f) (Bonus points) Given a circle, its center, and a point off the circle, construct the line tangent to the circle through the given point.
Any submitted solution should be verifiable through various properties of Euclidean geometry - no "eyeballing" allowed. Part f) is for bonus points only - any solution that correctly solves a) through e) will be counted as a correct solution.