Do you mean this symbol ∈ (or backwards 3) if so, it means is an element of; Also, ∉ (with strikethrough) (or backwards 3 with strikethrough) is the symbol for "is not an element of" used in set membership. See also Element (mathematics) and Set (mathematics)
If all the elements in set A are also elements of set B, then set A is a subset of set B.
A variance is a measure of how far a set of numbers is spread out around its mean.
The difference between the highest and lowest number in the set
A joint set is a dumb thing in the dumber thing mathematics
A matrix in mathematics is a rectangular array of quantities or expressions set out by rows and columns.
In mathematics, the range is the difference between the highest and lowest numbers in a set of data.
In mathematics it refers to a set of numbers which cannot be expressed as ratios of two integers.
Null set
The symbol "X" with a line over it is often used in mathematics to represent the average or arithmetic mean of a set of values. It is calculated by adding up all the values and dividing by the number of values in the set.
Yes the null set is a subset of every set.
a set having no elements, or only zeros as elements.