Math Problem Statement

Find the sum of the series: ∑(n=0 to ∞) x^(2n-1) / n!

Solution

The series provided in the image is:

n=0x2n1n!\sum_{n=0}^{\infty} \frac{x^{2n-1}}{n!}

Let's simplify and solve it.

Step 1: Recognizing the series

The given series is similar to the Maclaurin series of the exponential function:

ex=n=0xnn!e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!}

However, we notice that the power of xx in our series is 2n12n-1 instead of nn. This modification affects the structure.

Step 2: Rewriting the series

We can rewrite the power x2n1x^{2n-1} as:

n=0x2n1n!=1xn=0x2nn!\sum_{n=0}^{\infty} \frac{x^{2n-1}}{n!} = \frac{1}{x} \sum_{n=0}^{\infty} \frac{x^{2n}}{n!}

Factoring out x1x^{-1}, we now focus on summing the series n=0x2nn!\sum_{n=0}^{\infty} \frac{x^{2n}}{n!}.

Step 3: Recognizing a known series

This series:

n=0x2nn!\sum_{n=0}^{\infty} \frac{x^{2n}}{n!}

is actually the Maclaurin series of ex2e^{x^2}, because:

ex2=n=0(x2)nn!=n=0x2nn!e^{x^2} = \sum_{n=0}^{\infty} \frac{(x^2)^n}{n!} = \sum_{n=0}^{\infty} \frac{x^{2n}}{n!}

Step 4: Substituting back

Thus, the sum becomes:

1xex2\frac{1}{x} e^{x^2}

Final Answer:

n=0x2n1n!=ex2x\sum_{n=0}^{\infty} \frac{x^{2n-1}}{n!} = \frac{e^{x^2}}{x}

Let me know if you'd like further clarification or more details on the solution!


Here are 5 related questions to explore further:

  1. How would the series change if the exponent was 2n2n instead of 2n12n-1?
  2. Can this method be applied to other modifications of the exponential series?
  3. What happens to the sum if we replace n!n! with (2n)!(2n)! in the denominator?
  4. How is the solution different for series that involve odd powers of nn?
  5. How would you approach this problem if the summation index started at n=1n=1 instead of n=0n=0?

Tip: Understanding the Maclaurin series for common functions like exe^x can greatly simplify solving modified series problems like this one.

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Math Problem Analysis

Mathematical Concepts

Series
Exponential Functions
Maclaurin Series

Formulas

e^x = ∑(n=0 to ∞) x^n / n!

Theorems

Maclaurin Series

Suitable Grade Level

Grades 11-12, College