Which of the following are sets ? Justify your answer.
A collection of most dangerous animals of the world.
The collection of most dangerous animals of the world is not a well-defined collection because the criteria for determining the dangerousness of an animal can vary from person to person.
Hence, this collection is not a set.
State whether each of the following set is finite or infinite :
The set of letters in the English alphabet
Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$\varnothing \subset A$
Write the following sets in roster form :
$\mathrm{E} =$ The set of all letters in the world $\mathrm{TRIGONOMETRY}$
Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$1 \in A$
In the following state whether $A=B$ or not :
$A=\{a, b, c, d\} ; B=\{d, c, b, a\}$