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Part of NCERT 11 Mathematics
See sets in your world
Right now, sets are working behind the scenes:
Your WhatsApp groups? Each is a set of people.
Your Spotify 'Liked Songs'? A set of tracks.
Netflix recommendations? Sets of movies you might like.
Google search results? A set of matching web pages.
Every app, every database, every algorithm uses sets.
What makes a set a set?
For ANY collection to be a set, this must be true:
Can you clearly decide if something belongs? YES or NO?
No 'maybe'. No 'depends'. No opinions.
Everyone must agree on what's in and what's out.
This is called being well-defined.
Essential terms and symbols
Writing sets by listing
The simplest way to write a set.
List all elements inside curly braces { }.
Separate with commas.
Format:
Writing sets by describing properties
Instead of listing, describe what makes something a member.
Format:
Or:
The colon (:) or bar (|) means 'such that'
Read: 'The set of all x such that [property] is true'
Convert between set-builder and roster form
The set in roster form is: