let a, b be Real; :: thesis: ( 0 < a & b < a implies b / a < 1 )
assume A1: a > 0 ; :: thesis: ( not b < a or b / a < 1 )
assume A2: b < a ; :: thesis: b / a < 1
assume b / a >= 1 ; :: thesis: contradiction
then (b / a) * a >= 1 * a by A1, Lm12;
hence contradiction by A1, A2, XCMPLX_1:87; :: thesis: verum