let H be LTL-formula; :: thesis: ( H is next implies H . 1 = 3 )
assume H is next ; :: thesis: H . 1 = 3
then consider H1 being LTL-formula such that
A1: H = 'X' H1 by Def18;
thus H . 1 = 3 by A1, FINSEQ_1:58; :: thesis: verum