Theorem nsstr 42534

Description: If it's not a subclass, it's not a subclass of a smaller one. (Contributed by Glauco Siliprandi, 26-Jun-2021.)

Assertion

Ref	Expression
nsstr	⊢ ((¬ 𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐵) → ¬ 𝐴 ⊆ 𝐶)

Proof of Theorem nsstr

Step	Hyp	Ref	Expression
1		sstr 3925	. . . 4 ⊢ ((𝐴 ⊆ 𝐶 ∧ 𝐶 ⊆ 𝐵) → 𝐴 ⊆ 𝐵)
2	1	ancoms 458	. . 3 ⊢ ((𝐶 ⊆ 𝐵 ∧ 𝐴 ⊆ 𝐶) → 𝐴 ⊆ 𝐵)
3	2	adantll 710	. 2 ⊢ (((¬ 𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐵) ∧ 𝐴 ⊆ 𝐶) → 𝐴 ⊆ 𝐵)
4		simpll 763	. 2 ⊢ (((¬ 𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐵) ∧ 𝐴 ⊆ 𝐶) → ¬ 𝐴 ⊆ 𝐵)
5	3, 4	pm2.65da 813	1 ⊢ ((¬ 𝐴 ⊆ 𝐵 ∧ 𝐶 ⊆ 𝐵) → ¬ 𝐴 ⊆ 𝐶)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 395   ⊆ wss 3883

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1799  ax-4 1813  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2110  ax-9 2118  ax-ext 2709

This theorem depends on definitions:  df-bi 206  df-an 396  df-tru 1542  df-ex 1784  df-sb 2069  df-clab 2716  df-cleq 2730  df-clel 2817  df-v 3424  df-in 3890  df-ss 3900

This theorem is referenced by:  mbfpsssmf  44205