Theorem imbi2 339

Description: Theorem *4.85 of [WhiteheadRussell] p. 122. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 19-May-2013.)

Assertion

Ref	Expression
imbi2	⊢ ((𝜑 ↔ 𝜓) → ((𝜒 → 𝜑) ↔ (𝜒 → 𝜓)))

Proof of Theorem imbi2

Step	Hyp	Ref	Expression
1		id 22	. 2 ⊢ ((𝜑 ↔ 𝜓) → (𝜑 ↔ 𝜓))
2	1	imbi2d 331	1 ⊢ ((𝜑 ↔ 𝜓) → ((𝜒 → 𝜑) ↔ (𝜒 → 𝜓)))

Syntax hints:   → wi 4   ↔ wb 197

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 198

This theorem is referenced by:  relexpindlem  14020  relexpind  14021  ifpbi2  38305  ifpbi3  38306  3impexpbicom  39177  sbcim2g  39240  3impexpbicomVD  39580  sbcim2gVD  39599  csbeq2gVD  39616  con5VD  39624  hbexgVD  39630  ax6e2ndeqVD  39633  2sb5ndVD  39634  ax6e2ndeqALT  39655  2sb5ndALT  39656