# New post in Elementary-set-theory

July 26th, 2022

## What is countably infinite set?

January 15th, 2023

## prove that 2 closed interval sets have equal cardinalities

December 28th, 2022

July 23rd, 2022

## Is there an injective function from the set of natural numbers N to the set of rational numbers Q, and viceversa?

August 18th, 2022

## How is the set of rational numbers countably infinite?

October 28th, 2022

## Which of the following sets are equal?

November 10th, 2022

July 23rd, 2022

## If $A$ and $B$ are sets, and $A$ is element of $B$

August 14th, 2022

July 22nd, 2022

July 31st, 2022

July 22nd, 2022

July 29th, 2022

July 29th, 2022

August 1st, 2022

## Showing that a set is countably infinite by defining a bijection between $\Bbb N$ and that set.

November 16th, 2020

August 1st, 2022

April 3rd, 2020

August 1st, 2022

## Is every point of rational number boundary point?

January 25th, 2020

May 28th, 2020

August 1st, 2022

August 1st, 2022

March 25th, 2020

August 1st, 2022

August 1st, 2022

March 23rd, 2020

## Show that a relation is equivalent if it is both reflexive and cyclic.

September 27th, 2021

August 1st, 2022

July 1st, 2020