let z, z1, z2 be Element of F_Complex; :: thesis: ( z1 <> 0. F_Complex & z2 <> 0. F_Complex implies (z1 ") * (z / z2) = z / (z1 * z2) )
reconsider z19 = z1, z29 = z2, z9 = z as Element of COMPLEX by Def1;
assume A1: z1 <> 0. F_Complex ; :: thesis: ( not z2 <> 0. F_Complex or (z1 ") * (z / z2) = z / (z1 * z2) )
assume A2: z2 <> 0. F_Complex ; :: thesis: (z1 ") * (z / z2) = z / (z1 * z2)
then A3: z1 * z2 <> 0. F_Complex by A1, VECTSP_1:12;
A4: z9 / z29 = z / z2 by A2, Th6;
z1 " = z19 " by A1, Th5;
hence (z1 ") * (z / z2) = z9 / (z19 * z29) by A4, XCMPLX_1:220
.= z / (z1 * z2) by A3, Th6 ;
:: thesis: verum