9/13/.2011

P(k1 k2)=p(k1)*p(k2/k1) if k1 , k2 are dependent.

if k1 , k2 are independent p(k2/k1)=p(k2) i.e k2 doesnot depend on the occurrence of k1 

hence we have 

P(k1 k2)=p(k1)*p(k2)

Anuj