for a, b, c being Real for Iac, Icb being non emptycompactSubset of REAL st a <= c & c <= b & Iac =[.a,c.] & Icb =[.c,b.] holds for Dac being Division of Iac for Dcb being Division of Icb for i, j being Nat st i indom Dac & j indom Dcb holds ( ( i <len Dac implies Dac . i < Dcb . j ) & ( i =len Dac & c < Dcb . 1 implies Dac . i < Dcb . j ) & ( Dcb . 1 = c implies Dac .(len Dac)= Dcb . 1 ) )