Theorem cbviotav

Description: Change bound variables in a description binder. Usage of this theorem is discouraged because it depends on ax-13 . Use the weaker cbviotavw when possible. (Contributed by Andrew Salmon, 1-Aug-2011) (New usage is discouraged.)

	Ref	Expression
Hypothesis	cbviotav.1	|- ( x = y -> ( ph <-> ps ) )
Assertion	cbviotav	|- ( iota x ph ) = ( iota y ps )

Proof

Step	Hyp	Ref	Expression
1		cbviotav.1	|- ( x = y -> ( ph <-> ps ) )
2		nfv	|- F/ y ph
3		nfv	|- F/ x ps
4	1 2 3	cbviota	|- ( iota x ph ) = ( iota y ps )