7단원


7단원

조합론적 증명(combinatorial proof) https://en.wikipedia.org/wiki/Combinatorial_proof A proof by double counting. A combinatorial identity is proven by counting the number of elements of some carefully chosen set in two different ways to obtain the different expressions in the identity. Since those expressions count the same objects, they must be equal to each other and thus the identity is established..


원문링크 : 7단원