Description: The complement of an element of a sigma-algebra is in the sigma-algebra. (Contributed by Glauco Siliprandi, 26-Jun-2021)
Ref | Expression | ||
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Hypotheses | saldifcld.1 | |
|
saldifcld.2 | |
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Assertion | saldifcld | |
Step | Hyp | Ref | Expression |
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1 | saldifcld.1 | |
|
2 | saldifcld.2 | |
|
3 | saldifcl | |
|
4 | 1 2 3 | syl2anc | |