Description: The Lebesgue measure (for the zero dimensional space of reals) of every measurable set is zero. (Contributed by Glauco Siliprandi, 8-Apr-2021)
Ref | Expression | ||
---|---|---|---|
Hypothesis | von0val.1 | ⊢ ( 𝜑 → 𝐴 ∈ dom ( voln ‘ ∅ ) ) | |
Assertion | von0val | ⊢ ( 𝜑 → ( ( voln ‘ ∅ ) ‘ 𝐴 ) = 0 ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | von0val.1 | ⊢ ( 𝜑 → 𝐴 ∈ dom ( voln ‘ ∅ ) ) | |
2 | 0fin | ⊢ ∅ ∈ Fin | |
3 | 2 | a1i | ⊢ ( 𝜑 → ∅ ∈ Fin ) |
4 | 3 1 | mblvon | ⊢ ( 𝜑 → ( ( voln ‘ ∅ ) ‘ 𝐴 ) = ( ( voln* ‘ ∅ ) ‘ 𝐴 ) ) |
5 | 3 1 | vonmblss2 | ⊢ ( 𝜑 → 𝐴 ⊆ ( ℝ ↑m ∅ ) ) |
6 | 5 | ovn0val | ⊢ ( 𝜑 → ( ( voln* ‘ ∅ ) ‘ 𝐴 ) = 0 ) |
7 | 4 6 | eqtrd | ⊢ ( 𝜑 → ( ( voln ‘ ∅ ) ‘ 𝐴 ) = 0 ) |