Metamath Proof Explorer


Theorem meaunle

Description: The measure of the union of two sets is less than or equal to the sum of the measures, Property 112C (c) of Fremlin1 p. 15. (Contributed by Glauco Siliprandi, 17-Aug-2020)

Ref Expression
Hypotheses meaunle.1 ( 𝜑𝑀 ∈ Meas )
meaunle.2 𝑆 = dom 𝑀
meaunle.3 ( 𝜑𝐴𝑆 )
meaunle.4 ( 𝜑𝐵𝑆 )
Assertion meaunle ( 𝜑 → ( 𝑀 ‘ ( 𝐴𝐵 ) ) ≤ ( ( 𝑀𝐴 ) +𝑒 ( 𝑀𝐵 ) ) )

Proof

Step Hyp Ref Expression
1 meaunle.1 ( 𝜑𝑀 ∈ Meas )
2 meaunle.2 𝑆 = dom 𝑀
3 meaunle.3 ( 𝜑𝐴𝑆 )
4 meaunle.4 ( 𝜑𝐵𝑆 )
5 undif2 ( 𝐴 ∪ ( 𝐵𝐴 ) ) = ( 𝐴𝐵 )
6 5 eqcomi ( 𝐴𝐵 ) = ( 𝐴 ∪ ( 𝐵𝐴 ) )
7 6 fveq2i ( 𝑀 ‘ ( 𝐴𝐵 ) ) = ( 𝑀 ‘ ( 𝐴 ∪ ( 𝐵𝐴 ) ) )
8 7 a1i ( 𝜑 → ( 𝑀 ‘ ( 𝐴𝐵 ) ) = ( 𝑀 ‘ ( 𝐴 ∪ ( 𝐵𝐴 ) ) ) )
9 1 2 dmmeasal ( 𝜑𝑆 ∈ SAlg )
10 saldifcl2 ( ( 𝑆 ∈ SAlg ∧ 𝐵𝑆𝐴𝑆 ) → ( 𝐵𝐴 ) ∈ 𝑆 )
11 9 4 3 10 syl3anc ( 𝜑 → ( 𝐵𝐴 ) ∈ 𝑆 )
12 disjdif ( 𝐴 ∩ ( 𝐵𝐴 ) ) = ∅
13 12 a1i ( 𝜑 → ( 𝐴 ∩ ( 𝐵𝐴 ) ) = ∅ )
14 1 2 3 11 13 meadjun ( 𝜑 → ( 𝑀 ‘ ( 𝐴 ∪ ( 𝐵𝐴 ) ) ) = ( ( 𝑀𝐴 ) +𝑒 ( 𝑀 ‘ ( 𝐵𝐴 ) ) ) )
15 8 14 eqtrd ( 𝜑 → ( 𝑀 ‘ ( 𝐴𝐵 ) ) = ( ( 𝑀𝐴 ) +𝑒 ( 𝑀 ‘ ( 𝐵𝐴 ) ) ) )
16 1 2 11 meaxrcl ( 𝜑 → ( 𝑀 ‘ ( 𝐵𝐴 ) ) ∈ ℝ* )
17 1 2 4 meaxrcl ( 𝜑 → ( 𝑀𝐵 ) ∈ ℝ* )
18 1 2 3 meaxrcl ( 𝜑 → ( 𝑀𝐴 ) ∈ ℝ* )
19 difssd ( 𝜑 → ( 𝐵𝐴 ) ⊆ 𝐵 )
20 1 2 11 4 19 meassle ( 𝜑 → ( 𝑀 ‘ ( 𝐵𝐴 ) ) ≤ ( 𝑀𝐵 ) )
21 16 17 18 20 xleadd2d ( 𝜑 → ( ( 𝑀𝐴 ) +𝑒 ( 𝑀 ‘ ( 𝐵𝐴 ) ) ) ≤ ( ( 𝑀𝐴 ) +𝑒 ( 𝑀𝐵 ) ) )
22 15 21 eqbrtrd ( 𝜑 → ( 𝑀 ‘ ( 𝐴𝐵 ) ) ≤ ( ( 𝑀𝐴 ) +𝑒 ( 𝑀𝐵 ) ) )