theorem
  -<*c*> = <*-c*>
proof
  reconsider s=c as Element of COMPLEX by XCMPLX_0:def 2;
  -<*s*> = <*compcomplex.s*> by FINSEQ_2:35
        .= <*-c*> by BINOP_2:def 1;
  hence thesis;
end;
