1. The definition of a circle is all the points in a plane that are at some radius r from a given point (the circle center). That is what you have, with a radius of 2 cm.
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2. Parallel lines are the same distance apart everywhere. Each line will have two parallel lines at some given distance from it, one on each side. Here, the separation distance from AB is 1 cm, so your locus of points is the two lines parallel AB that are 1 cm from it on either side.
