Before working with definite integrals and infinite series, you need to understand sigma notation. Sigma notation is just a compact way to write sums, i.e. adding a sequence of numbers or terms.
A term using sigma notation is called a series or summation (sum for short).
For example, if we have \( 1 + 2 + 3 + 4 + 5 \), we can write this as \(\displaystyle{ \sum_{i=1}^{5}{i} }\). Let's look at each part of this notation.
1. First, \(\sum\) just means to add. This is the uppercase Greek letter sigma.
2. The letter i is called the index. It is usually an integer. You will also see other variables used here like n or k.
3. The assignment \(i=1\) under the sigma gives you the starting value of the index and the index letter.
4. The number above the sigma tells you the ending value of the index. We don't need to repeat 'i=' here. The index is incremented by 1 until it reaches in the ending value. It includes the ending value. For infinite series, you will find \(\infty\) above the sigma.
5. In this sum, we just have i, so we iterate over the index and add up the results.
In general, we add up more interesting things than just integers. So you will sometimes see the notation \(\displaystyle{ \sum_{i=1}^{n}{a_i} }\) where \(a_i\) is some term involving the index i.
Before we go on, let's watch a video. This is a good overview of sigma notation. In this video, he starts by explaining the general notation and then he works several examples.
video by PatrickJMT 

Practice
Unless otherwise instructed, evaluate these sums. Give your answers in exact form.
Evaluate \(\displaystyle{ \sum_{n=1}^{5}{ (2n+3) } }\)
Problem Statement 

Evaluate \(\displaystyle{ \sum_{n=1}^{5}{ (2n+3) } }\)
Solution 

video by The Organic Chemistry Tutor 

close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{ \sum_{n=1}^{6}{ n^2 } }\)
Problem Statement 

Evaluate \(\displaystyle{ \sum_{n=1}^{6}{ n^2 } }\)
Solution 

video by The Organic Chemistry Tutor 

close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{ \sum_{k=0}^{4}{ \frac{1}{k^2+1} } }\)
Problem Statement 

Evaluate \(\displaystyle{ \sum_{k=0}^{4}{ \frac{1}{k^2+1} } }\)
Final Answer 

158/85
Problem Statement 

Evaluate \(\displaystyle{ \sum_{k=0}^{4}{ \frac{1}{k^2+1} } }\)
Solution 

A minute or two into this video he realizes that he didn't write down one of the terms and he posts a note about it. Even though the final answer in the video is incorrect, his procedure is good to watch.
video by The Organic Chemistry Tutor 

Final Answer 

158/85 
close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{ \sum_{n=1}^{3}{ 2^n } }\)
Problem Statement 

Evaluate \(\displaystyle{ \sum_{n=1}^{3}{ 2^n } }\)
Solution 

video by The Organic Chemistry Tutor 

close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{\sum_{k=1}^{6}{\frac{1}{k^2}}}\)
Problem Statement 

Evaluate \(\displaystyle{\sum_{k=1}^{6}{\frac{1}{k^2}}}\)
Solution 

video by Krista King Math 

close solution

Log in to rate this practice problem and to see it's current rating. 

Write\(\displaystyle{\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+}\) \(\displaystyle{\frac{1}{16}+}\) \(\displaystyle{\frac{1}{32}+}\) \(\displaystyle{\frac{1}{64}}\) in sigma notation.
Problem Statement 

Write\(\displaystyle{\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+}\) \(\displaystyle{\frac{1}{16}+}\) \(\displaystyle{\frac{1}{32}+}\) \(\displaystyle{\frac{1}{64}}\) in sigma notation.
Solution 

video by Krista King Math 

close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{\sum_{r=1}^{8}{(r1)(r+2)}}\)
Problem Statement 

Evaluate \(\displaystyle{\sum_{r=1}^{8}{(r1)(r+2)}}\)
Solution 

video by Krista King Math 

close solution

Log in to rate this practice problem and to see it's current rating. 

Evaluate \(\displaystyle{\sum_{i=1}^{4}{(1)^i i^2}}\)
Problem Statement 

Evaluate \(\displaystyle{\sum_{i=1}^{4}{(1)^i i^2}}\)
Solution 

video by PatrickJMT 

close solution

Log in to rate this practice problem and to see it's current rating. 

You CAN Ace Calculus
To bookmark this page and practice problems, log in to your account or set up a free account.
Single Variable Calculus 

MultiVariable Calculus 

Differential Equations 

Precalculus 

Do you have a practice problem number but do not know on which page it is found? If so, enter the number below and click 'page' to go to the page on which it is found or click 'practice' to be taken to the practice problem.
 
free ideas to save on bags & supplies 

Help Keep 17Calculus Free 

The 17Calculus and 17Precalculus iOS and Android apps are no longer available for download. If you are still using a previously downloaded app, your app will be available until the end of 2020, after which the information may no longer be available. However, do not despair. All the information (and more) is now available on 17calculus.com for free. 
How to Develop a Brilliant Memory Week by Week: 50 Proven Ways to Enhance Your Memory Skills 

Practice Instructions
Unless otherwise instructed, evaluate these sums. Give your answers in exact form.