A mathematical symbol, I don't know what it means. I'm confused and I can't find it anywhere. I'm a senior one, and I'm doing a problem about assembly.

Hello, I'm glad to answer your question! This is a mathematical symbol for collective learning in senior high schools.

Inclusion is the relationship between sets, also called subset relationship. Example A={ 1, 2}, B={ 1, 2, 3}

Then 1 ∈ A, 2 ∈ A, 3 ∈ b.

Answer? B

Contained in:, horizontally contained in,? The following ≠ is really included in.

Answer? B means that all elements of a belong to B.

Answer? B stands for a? B but a ≠ B.

Attribution is the relationship between elements and sets. For example, the element A belongs to the set A and is marked as A ∈ A.

Attribution symbol: ∈, used between elements and sets.

I hope I can help you, thank you!