Operations on Sets
Intersection
The set of elements that two sets share, written A ∩ B.
| English | Intersection |
|---|---|
| Bahasa Melayu | Persilangan |
| 中文 | 交集 |
How it is used
If A = {1, 2, 3, 4} and B = {2, 4, 6}, then A ∩ B = {2, 4}, because only 2 and 4 belong to both sets.
Where it shows up in SPM
In the Operations on Sets chapter (Form 4). In Paper 1 as multiple-choice listing A ∩ B, and in Paper 2 when a Venn diagram gives n(A ∩ B) and you use n(A ∪ B) = n(A) + n(B) − n(A ∩ B).
Don't confuse it with
Open the chapter: Operations on Sets →
Frequently asked questions
What if the two sets have nothing in common?
Then their intersection is the empty set, written A ∩ B = { } or ∅. For example, {1, 3, 5} ∩ {2, 4, 6} = ∅ because no number is in both.
Such sets are called disjoint.
Does the order matter, is A ∩ B the same as B ∩ A?
No, the order does not matter. Intersection is commutative, so A ∩ B = B ∩ A always.
With A = {1, 2, 4} and B = {2, 4, 8}, both give {2, 4}. You may list the shared elements starting from either set.