*in which meet the orthogonal group and we rotate and reflect in two and three dimensions.
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# action

# Groups Lecture 16

*in which we learn about the symmetry groups of polyhedra, and start exploring conjugacy classes in the symmetric groups .
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# Groups Lecture 19

*in which we act with matrices on vectors and on matrices, and meet the orthogonal group.
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# Groups Lecture 16

*in which we prove Cauchy’s theorem and revisit the symmetric groups.
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