Metamath Proof Explorer

Theorem uneq1d

Description: Deduction adding union to the right in a class equality. (Contributed by NM, 29-Mar-1998)

Ref Expression
Hypothesis uneq1d.1 φ A = B
Assertion uneq1d φ A C = B C


Step Hyp Ref Expression
1 uneq1d.1 φ A = B
2 uneq1 A = B A C = B C
3 1 2 syl φ A C = B C