Discrete mathematics. Sets
What is a set? A set is a group of “objects” People in a class: { Alice, Bob, Chris } Classes offered by a department: { CS 101, CS 202, … } Colors of a rainbow: { red, orange, yellow, green, blue, purple } States of matter { solid, liquid, gas, plasma } States in the US: { Alabama, Alaska, Virginia, … } Sets can contain non-related elements: { 3, a, red, Virginia } Although a set can contain (almost) anything, we will most often use sets of numbers All positive numbers less than or equal to 5: {1, 2, 3, 4, 5} A few selected real numbers: { 2.1, π, 0, -6.32, e } Set properties 1 Order does not matter We often write them in order because it is easier for humans to understand it that way {1, 2, 3, 4, 5} is equivalent to {3, 5, 2, 4, 1} Sets are notated with curly brackets