Answer:
a) Definition of sequence of real numbers: A sequence of real number is the function from set of natural number to the set of real numbers. i.e.
f: N → R
Example:
![S_(n)=(1)/(n)](https://img.qammunity.org/2020/formulas/mathematics/college/4koab4ms00ai9ln7tu7fcm77xd4x657tde.png)
![S_(n)=(n)/(n+1)](https://img.qammunity.org/2020/formulas/mathematics/college/1mzzb6f2nib9dpp3hzpohx3ifv1vm0jdvh.png)
b) Definition of convergent sequence: A sequence is said to be convergent if for very large value of n, function will give the finite value.
Example:
![S_(n)=(1)/(n)](https://img.qammunity.org/2020/formulas/mathematics/college/4koab4ms00ai9ln7tu7fcm77xd4x657tde.png)
![S_(n)=(n)/(n+1)](https://img.qammunity.org/2020/formulas/mathematics/college/1mzzb6f2nib9dpp3hzpohx3ifv1vm0jdvh.png)
c) Definition of Cauchy sequence: A sequence is said to be Cauchy Sequence if terms of sequence get arbitrary close to one another.