## What is Infinity?

Infinity in mathematical terms is a concept that represents an unbounded quantity or an endless extent. It is not a specific number, but rather a symbol (*∞*) used to denote a quantity that is larger than any finite number.

The concept of infinity has been used in various forms throughout the history of mathematics, and its understanding has evolved over time. The ancient Greeks, such as __Zeno of Elea__, explored paradoxes related to infinite divisibility and the concept of infinity. However, the formal treatment of infinity and its incorporation into mathematical notation began in the 17th century.

The concept of infinity was introduced more rigorously by mathematicians like __John Wallis__ and __Georg Cantor__. Wallis used the symbol *'∞'* for the first time in 1655 to represent infinity, and Cantor, in the late 19th and early 20th centuries, developed a comprehensive theory of infinite sets, defining different sizes of infinity and introducing concepts like countable and uncountable infinities.

**Note:** It's important to note that while mathematicians have developed a formal framework for dealing with infinity, it remains a theoretical concept and not a specific, tangible quantity.

### Infinity in Math:

Here are a few examples of how infinity might appear in mathematical formulas or expressions:

**1.** __Limit__:

`lim _{x}→ ∞f(x)`

**⤏** This represents the limit of the function `f(x)` as *x* approaches infinity.

**2.** __Series__:

${\sum}_{n=1}^{\mathrm{\infty}}{a}_{n}$

**⤏** This represents an infinite series where `a _{n}` is a sequence of numbers.

**3.** __Set Notation__:

`{x ∣ x > a}` where *a* is any real number

**⤏** This represents the set of all real numbers greater than *a*, extending to infinity.

**4.** __Interval Notation__:

`(a, ∞)`

**⤏** This represents an open interval where the endpoint is infinity.

**Note:** It's important to note that infinity is not a real number, and arithmetic operations involving infinity should be treated with caution.

The concept of infinity is often used in calculus, analysis, and other branches of mathematics to describe unbounded behavior or limits that extend indefinitely.

__The Man Who Knew Infinity__?

"The Man Who Knew Infinity" refers to the renowned Indian mathematician __Srinivasa Ramanujan__. The title is derived from a biography of the same name, written by Robert Kanigel and published in 1991. The book narrates the life and mathematical contributions of Ramanujan.

Ramanujan's work primarily involved number theory, infinite series, and mathematical analysis. In 1913, he began corresponding with British mathematician G. H. Hardy, which led to his invitation to Cambridge University. Ramanujan spent several years working with Hardy and Littlewood at Cambridge, contributing significantly to mathematical research.

**•** One of his notable contributions involves a beautiful formula for the infinite series related to **π** (pi), which is sometimes referred to as Ramanujan's pi formula.

• __The formula states__:

• Kindly rotate your mobile screen to show the formula.

$\frac{1}{\pi}=\frac{2\sqrt{2}}{2}\cdot \frac{\sqrt{2+\sqrt{2}}}{2}\cdot \frac{\sqrt{2+\sqrt{2+\sqrt{2}}}}{2}\cdot \frac{\sqrt{2+\sqrt{2+\sqrt{2+\sqrt{2}}}}}{2}\cdot \dots $

This formula is an example of an infinite nested radical, where each term involves a square root. It converges to the reciprocal of π, and it provides an elegant and surprising way to express the reciprocal of π using nested square roots. The infinite nesting of square roots makes it a fascinating and distinctive formula associated with Ramanujan's work.

It's important to note that Ramanujan's contributions to mathematics were extensive, and he developed many results and formulas across different areas of the subject. The formula mentioned here is just one example of his remarkable insights into mathematical structures.

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