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Imagine a sheet of paper cut into a pentagon. On the arbitrarily designated "FRONT" size, label the vertices "a", "b", "c", "d" and "e" in a clockwise direction. On the reverse ("BACK") side, label the vertices "α", "β", "γ", "δ" and "&epsilon", corresponding to "a", "b", "c", "d" & "e", respectively. This labeling is counter-clockwise. The dihedral group of the pentagon is the group of all symmetries of the pentagon. This includes rotations through multiples of 2π/5 degrees, reflections about five different axes and flips about five different axes. Axisd, for example, is the line through vertex "d" that intersects the side of the pentagon opposite to it at right angles. In this case, the side connects vertices "a" and "b". Define
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![]() | Michael Zuker Department of Mathematical Sciences Rensselaer Polytechnic Institute Spring 2008 |