theorem Th44:
  symmetric_3(1,1,-1,0,0,0) is invertible Matrix of 3,F_Real &
  (symmetric_3(1,1,-1,0,0,0))~ = symmetric_3(1,1,-1,0,0,0)
  proof
A1: symmetric_3(1,1,-1,0,0,0) is_reverse_of symmetric_3(1,1,-1,0,0,0)
      by Th43,MATRIX_6:def 2;
    thus symmetric_3(1,1,-1,0,0,0) is invertible Matrix of 3,F_Real
      by Th43,MATRIX_6:def 2,MATRIX_6:def 3;
    hence (symmetric_3(1,1,-1,0,0,0))~ = symmetric_3(1,1,-1,0,0,0)
      by A1,MATRIX_6:def 4;
  end;
