This is a collection of some revision notes. They include topics discussed in first three sessions of Combinatorics Course at Cheenta (Faculty: Ashani Dasgupta).

combinatorics 1 (work sheet)

Study of symmetry in geometry is greatly facilitated by combinatorial methodsThere are 6 symmetries of an equilateral triangle (=3! permutations of 3 things) There are 8 symmetries of a square (8 out of 4! permutations of 4 things are used up) All 24 symmetries (including orientations) of a tetrahedron account for 4! permutations of 4 things Cycle notation helps in exploiting permutationsLength of a cycle equals it’s order Bijection Principle helps to count sets which are otherwise difficult to count.Number of non negative integer solutions of a + b + c + d = n is We use balls and bars technique to do this Partitions Conjugate Partitions and Ferrar’s diagram Catalan Numbers Some Useful Links:

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