Theorem cmcmii

Description: Commutation is symmetric. Theorem 2(v) of Kalmbach p. 22. (Contributed by NM, 7-Aug-2004) (New usage is discouraged.)

	Ref	Expression
Hypotheses	pjoml2.1	$$⊢A\in {\mathbf{C}}_{\mathscr{H}}$$
	pjoml2.2	$$⊢B\in {\mathbf{C}}_{\mathscr{H}}$$
	cmcmi.1	$$⊢A{𝐶}_{\mathscr{H}}B$$
Assertion	cmcmii	$$⊢B{𝐶}_{\mathscr{H}}A$$

Proof

Step	Hyp	Ref	Expression
1		pjoml2.1	$$⊢A\in {\mathbf{C}}_{\mathscr{H}}$$
2		pjoml2.2	$$⊢B\in {\mathbf{C}}_{\mathscr{H}}$$
3		cmcmi.1	$$⊢A{𝐶}_{\mathscr{H}}B$$
4	1 2	cmcmi	$$⊢A{𝐶}_{\mathscr{H}}B\leftrightarrow B{𝐶}_{\mathscr{H}}A$$
5	3 4	mpbi	$$⊢B{𝐶}_{\mathscr{H}}A$$