reserve x,y,X,Y for set;
reserve C for non empty set;
reserve c for Element of C;
reserve f,f1,f2,f3,g,g1 for PartFunc of C,COMPLEX;
reserve r1,r2,p1 for Real;
reserve r,q,cr1,cr2 for Complex;

theorem
  |.f1/f2.| = |.f1.|/|.f2.|
proof
  thus |.f1/f2.| = |.f1(#)(f2^).| by Th38
    .= |.f1.|(#)|.(f2^).| by Th29
    .= |.f1.|(#)((|.f2.|)^) by Th37
    .= |.f1.|/|.f2.| by RFUNCT_1:31;
end;
