# Groups Lecture 19

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

# Groups Lecture 16

in which we learn about the symmetry groups of polyhedra, and start exploring conjugacy classes in the symmetric groups $S_n$.

# Groups Lecture 19

in which we act with matrices on vectors and on matrices, and meet the orthogonal group.

# Groups Lecture 16

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