Theorem 2.5 Supposing < X; ; 0 > is a limited BCI-algebra, 2 lc
X, 2 ld X. Then we have
) c d:
Proof.Because , 9x1; x2; : : : ; xn 2 X s:t: x1 x2 xn
. As x1, 9; 2 L(X) s:t: = x1; x1 = . Supposing x1 2 le, then
we have the follows
c = (0 (0 )) (0 (0 )) = 0 (0 ( )) = 0 (0 x1) = e
e = (0 (0 x1)) (0 (0 )) = 0 (0 (x1 )) = 0 (0 ) = c
which means c e. Similarly, this theorem could be proved.
In these two theorems, replacing with , they will be also right.They
are the more particular forms.
More results will be given in the next section.