Theorem coeq12i

Description: Equality inference for composition of two classes. (Contributed by FL, 7-Jun-2012)

	Ref	Expression
Hypotheses	coeq12i.1	$$⊢A=B$$
	coeq12i.2	$$⊢C=D$$
Assertion	coeq12i	$$⊢A\circ C=B\circ D$$

Proof

Step	Hyp	Ref	Expression
1		coeq12i.1	$$⊢A=B$$
2		coeq12i.2	$$⊢C=D$$
3	1	coeq1i	$$⊢A\circ C=B\circ C$$
4	2	coeq2i	$$⊢B\circ C=B\circ D$$
5	3 4	eqtri	$$⊢A\circ C=B\circ D$$