Theorem ublemc1 728

Description: Commutation theorem for biimplication. (Contributed by NM, 19-Sep-1998.)

Assertion

Ref	Expression
ublemc1	a C (a ≡ b)

Proof of Theorem ublemc1

Step	Hyp	Ref	Expression
1		combi 485	1 a C (a ≡ b)

Syntax hints:   C wc 3   ≡ tb 5

This theorem was proved from axioms:  ax-a1 30  ax-a2 31  ax-a3 32  ax-a4 33  ax-a5 34  ax-r1 35  ax-r2 36  ax-r4 37  ax-r5 38  ax-r3 439

This theorem depends on definitions:  df-b 39  df-a 40  df-t 41  df-f 42  df-le1 130  df-le2 131  df-c1 132  df-c2 133

This theorem is referenced by:  ublemc2  729