Theorem ndsubeqd-P7 856

Description: Natural Deduction: Equality Substitution Rule (dual). †

Hypotheses

Ref	Expression
ndsubeqd-P7.1	⊢ (𝛾 → 𝑠 = 𝑡)
ndsubeqd-P7.2	⊢ (𝛾 → 𝑢 = 𝑤)

Assertion

Ref	Expression
ndsubeqd-P7	⊢ (𝛾 → (𝑠 = 𝑢 ↔ 𝑡 = 𝑤))

Proof of Theorem ndsubeqd-P7

Step	Hyp	Ref	Expression
1		ndsubeqd-P7.1	. . 3 ⊢ (𝛾 → 𝑠 = 𝑡)
2	1	ndsubeql-P7.22a 847	. 2 ⊢ (𝛾 → (𝑠 = 𝑢 ↔ 𝑡 = 𝑢))
3		ndsubeqd-P7.2	. . 3 ⊢ (𝛾 → 𝑢 = 𝑤)
4	3	ndsubeqr-P7.22b 848	. 2 ⊢ (𝛾 → (𝑡 = 𝑢 ↔ 𝑡 = 𝑤))
5	2, 4	bitrns-P3.33c 302	1 ⊢ (𝛾 → (𝑠 = 𝑢 ↔ 𝑡 = 𝑤))

Syntax hints:   = wff-equals 6   → wff-imp 10   ↔ wff-bi 104

This theorem was proved from axioms:  ax-L1 11  ax-L2 12  ax-L3 13  ax-MP 14  ax-GEN 15  ax-L4 16  ax-L5 17  ax-L6 18  ax-L7 19

This theorem depends on definitions:  df-bi-D2.1 107  df-and-D2.2 133  df-or-D2.3 145  df-true-D2.4 155  df-rcp-AND3 161  df-exists-D5.1 596

This theorem is referenced by:  ndsubeqd-P7.RC  893  ndsubeqd-P7.CL  913