Theorem 3brtr4i

Description: Substitution of equality into both sides of a binary relation. (Contributed by NM, 11-Aug-1999)

	Ref	Expression
Hypotheses	3brtr4.1	$$⊢ARB$$
	3brtr4.2	$$⊢C=A$$
	3brtr4.3	$$⊢D=B$$
Assertion	3brtr4i	$$⊢CRD$$

Proof

Step	Hyp	Ref	Expression
1		3brtr4.1	$$⊢ARB$$
2		3brtr4.2	$$⊢C=A$$
3		3brtr4.3	$$⊢D=B$$
4	2 1	eqbrtri	$$⊢CRB$$
5	4 3	breqtrri	$$⊢CRD$$