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 methods
- There 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 permutations
- Length 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
- Conjugate Partitions and Ferrar’s diagram
- Catalan Numbers