Aljabar sigma itu apa sih? Jelaskan dalam bahasa sunda ya

Dina matematika, aljabar σ (atawa widang σ) X pikeun sasét S hartina anggota subsét S nu katutup ku sét operasi-operasi nu bisa diitung; aljabar σ utamana dipaké pikeun nangtukeun ukuran S. Ieu konsép penting dina analisis matematika jeung téori probabilitas.

Sacara formal, X kaasup aljabar σ mun jeung ukur mun (jika dan hanya jika, if and only if) miboga pasipatan di handap ieu:

The empty set is in X,

If E is in X then so is the complement of E.

If E1, E2, E3, ... is a sequence in X then their (countable) union is also in X.

From 1 and 2 it follows that S is in X; from 2 and 3 it follows that the σ-algebra is also closed under countable intersections (via De Morgan's laws).

An ordered pair (S, X), where S is a set and X is a σ-algebra over S, is called a méasurable space.