Theorem 2sbbii 2081

Description: Infer double substitution into both sides of a logical equivalence. (Contributed by AV, 30-Jul-2023.)

Hypothesis

Ref	Expression
sbbii.1	⊢ (𝜑 ↔ 𝜓)

Assertion

Ref	Expression
2sbbii	⊢ ([𝑡 / 𝑥][𝑢 / 𝑦]𝜑 ↔ [𝑡 / 𝑥][𝑢 / 𝑦]𝜓)

Proof of Theorem 2sbbii

Step	Hyp	Ref	Expression
1		sbbii.1	. . 3 ⊢ (𝜑 ↔ 𝜓)
2	1	sbbii 2080	. 2 ⊢ ([𝑢 / 𝑦]𝜑 ↔ [𝑢 / 𝑦]𝜓)
3	2	sbbii 2080	1 ⊢ ([𝑡 / 𝑥][𝑢 / 𝑦]𝜑 ↔ [𝑡 / 𝑥][𝑢 / 𝑦]𝜓)

Syntax hints:   ↔ wb 205  [wsb 2068

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1799  ax-4 1813

This theorem depends on definitions:  df-bi 206  df-sb 2069

This theorem is referenced by:  sbco4lem  2276  sbco4lemOLD  2277  ichcircshi  44794  ichbi12i  44800  icheq  44802  ichal  44806