reserve a,b,c,x,y,z for Real;

theorem
  0 < a implies a / sqrt a = sqrt a
proof
  assume
A1: 0 < a;
  then sqrt a <> 0^2 by Def2;
  hence a /sqrt a = (a*sqrt a) /(sqrt a)^2 by XCMPLX_1:91
    .= (sqrt a*a) /(1*a) by A1,Def2
    .= sqrt a/1 by A1,XCMPLX_1:91
    .= sqrt a;
end;
