Is there a formula for the square of an infinite sum?

In summary, the conversation discusses the possibility of finding a formula for the square of a general, convergent infinite sum. The Cauchy product is mentioned as a potential method, but it is noted that it may result in a double sum and may be difficult to use. The conversation ends with the acknowledgement that the Cauchy product is the only known method for finding the square of such a sum.
  • #1
Char. Limit
Gold Member
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Given a general, convergent infinite sum, say, one like this:

[tex]\sum_{n=0}^\infty a_n x^n[/tex]

Is there a formula for the square of such a sum? I looked at the Cauchy product, but I'd rather not get a double sum as an answer...
 
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  • #2
Char. Limit said:
Given a general, convergent infinite sum, say, one like this:

[tex]\sum_{n=0}^\infty a_n x^n[/tex]

Is there a formula for the square of such a sum? I looked at the Cauchy product, but I'd rather not get a double sum as an answer...

YMMV but I wouldn't call the Cauchy product a double sum. And if you wish to write the result as a power series, you're stuck with it. Those finite inner sums give the coefficients of ##x^n##. It is what it is.
 
  • #3
LCKurtz said:
YMMV but I wouldn't call the Cauchy product a double sum. And if you wish to write the result as a power series, you're stuck with it. Those finite inner sums give the coefficients of ##x^n##. It is what it is.

Aww, well I guess if I need to use the Cauchy product I'll have to figure out how to use it... thanks for the help though!
 

What is the "Square of an Infinite Sum"?

The Square of an Infinite Sum refers to the process of squaring an infinite series of numbers. An infinite series is a mathematical expression that has an infinite number of terms. Squaring an infinite sum involves multiplying each term in the series by itself and then adding all of the resulting terms together.

What is the formula for calculating the Square of an Infinite Sum?

The formula for calculating the Square of an Infinite Sum is (a + b + c + ...)^2 = a^2 + 2ab + 2ac + 2bc + 2ad + 2bd + 2cd + ... + b^2 + c^2 + ...

What is the significance of the Square of an Infinite Sum in mathematics?

The Square of an Infinite Sum is significant in mathematics because it is used to find the sum of an infinite series, which can have important applications in fields like physics, engineering, and economics. It also helps to understand the behavior of infinite series and their convergence or divergence.

How is the Square of an Infinite Sum related to the Binomial Theorem?

The Square of an Infinite Sum is related to the Binomial Theorem, which states that (a + b)^n = a^n + na^(n-1)b + (n(n-1)/2!)a^(n-2)b^2 + ... + b^n. By setting n = 2 in this formula, we get (a + b)^2 = a^2 + 2ab + b^2, which is the formula for calculating the Square of an Infinite Sum.

Are there any real-life applications of the Square of an Infinite Sum?

Yes, there are many real-life applications of the Square of an Infinite Sum. For example, it is used in physics to calculate the force of gravity between two objects, in finance to determine the value of investments with continuously compounded interest, and in computer science to estimate the running time of algorithms. It also has applications in probability and statistics, such as calculating the probability of getting a specific hand in a game of cards.

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