Menu

Math Lesson 12.4.5 - The Special Types of Infinite Series

Please provide a rating, it takes seconds and helps us to keep this resource free for all to use

[ 1 Votes ]

Welcome to our Math lesson on The Special Types of Infinite Series, this is the fifth lesson of our suite of math lessons covering the topic of Infinite Series Explained, you can find links to the other lessons within this tutorial and access additional Math learning resources below this lesson.

Working with the Special Types of Infinite Series

There are some special types of infinite series, which have many important applications in practice. Let's consider a few of them.

1. p-series

This is a special type of series which has the form

n - 11/np

The p-series is special because it is convergent for p > 1 and divergent for 0 < p ≤ 1. For example, for p = 2, we obtain

n - 11/np = n - 11/n2 = 1/12 + 1/22 + 1/32 + 1/42 + ⋯
= 1 + 1/4 + 1/9 + 1/16 + ⋯

Let's see what happens with the difference between two consecutive terms. Thus,

x1 - x2 = 1 - 1/4 = 4/4 - 3/4 = 3/4 = 0.75
x2 - x3 = 1/4 - 1/9 = 9/36 - 4/36 = 5/36 = 0.14
x3 - x4 = 1/9 - 1/16 = 16/144 - 9/144 = 7/144 = 0.05

Since the difference becomes smaller and smaller, this is a converging series.

On the other hand, if p < 1, for example for p = 0.5, we obtain

n - 11/np = n - 11/n0.5 = 1/10.5 + 1/20.5 + 1/30.5 + 1/40.5 + ⋯
= 1/√1 + 1/√2 + 1/√3 + 1/√4 = ⋯
= 1 + √2/2 + √3/3 + 1/2 + ⋯

It is true that the difference between terms decreases, but not so much so that to converge at a single point. In other words, this series is convergent to infinity, so practically it is divergent.

2. Harmonic series

They represent a special case of the p-series where p = 1, i.e

n - 11/np = n - 11/n1 = n - 11/n

In this way, we obtain for the harmonic series

H = n - 11/n = 1/1 + 1/2 + 1/3 + 1/4 + ⋯
= 1 + 1/2 + 1/3 + 1/4 + ⋯

This series is divergent, as it is impossible to reach to a limit point despite the decrease in the terms value with the increase of n.

3. Euler Series

This too, is a special series, which has the following form

Euler Series = n = 01/n!

We write the name of Euler Series (otherwise known as the Euler's Number) by e. It is worth to mention here that the counting of these series elements start from 0, not from 1. In this way, we obtain

e = n = 01/n! = 1/0! + 1/1! + 1/2! + 1/3! + 1/4! + ⋯
= 1/1 + 1/1 + 1/2 ∙ 1 + 1/3 ∙ 2 ∙ 1 + 1/4 ∙ 3 ∙ 2 ∙ 1 + ⋯
= 1 + 1 + 1/2 + 1/6 + 1/24 + ⋯
= 2 + 1/2 + 1/6 + 1/24 + ⋯

This is a converging series, as the non-constant ratio between two consecutive terms is always smaller than 1, and moreover, it decreases more rapidly than the converging geometric series

n = 11/2n

we have discussed earlier in this tutorial (we saw that this series converges at 1). In fact, the Euler series gives an irrational number, the first digits of which are as follows

e = 2.7182818284590…

This number is very important in a wide number of topics both in math and in physics.

More Infinite Series Explained Lessons and Learning Resources

Sequences and Series Learning Material
Tutorial IDMath Tutorial TitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
12.4Infinite Series Explained
Lesson IDMath Lesson TitleLessonVideo
Lesson
12.4.1Infinite and Finite Number Series
12.4.2Converging and Diverging Infinite Series
12.4.3Calculating an Infinite Geometric Series
12.4.4The Comparison Test of Convergence
12.4.5The Special Types of Infinite Series
12.4.6The Ratio Convergence Test
12.4.7The Root Convergence Test

Whats next?

Enjoy the "The Special Types of Infinite Series" math lesson? People who liked the "Infinite Series Explained lesson found the following resources useful:

  1. Special Types Of Infinite Series Feedback. Helps other - Leave a rating for this special types of infinite series (see below)
  2. Sequences and Series Math tutorial: Infinite Series Explained. Read the Infinite Series Explained math tutorial and build your math knowledge of Sequences and Series
  3. Sequences and Series Video tutorial: Infinite Series Explained. Watch or listen to the Infinite Series Explained video tutorial, a useful way to help you revise when travelling to and from school/college
  4. Sequences and Series Revision Notes: Infinite Series Explained. Print the notes so you can revise the key points covered in the math tutorial for Infinite Series Explained
  5. Sequences and Series Practice Questions: Infinite Series Explained. Test and improve your knowledge of Infinite Series Explained with example questins and answers
  6. Check your calculations for Sequences and Series questions with our excellent Sequences and Series calculators which contain full equations and calculations clearly displayed line by line. See the Sequences and Series Calculators by iCalculator™ below.
  7. Continuing learning sequences and series - read our next math tutorial: Working with Term-to-Term Rules in Sequences

Help others Learning Math just like you

Please provide a rating, it takes seconds and helps us to keep this resource free for all to use

[ 1 Votes ]

We hope you found this Math tutorial "Infinite Series Explained" useful. If you did it would be great if you could spare the time to rate this math tutorial (simply click on the number of stars that match your assessment of this math learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of math and other disciplines.

Sequences and Series Calculators by iCalculator™