# Blog

## Sum of Infinite Geometric Sequence

Hey math friends and happy Wednesday! Today we are going to take a look at how to find the sum of infinite geometric sequence (aka series) in summation notation. This may sound complicated, but lucky for us there is an already existing formula that is ready and easy for us to use! So, let’s get to it! Also, don’t forget to check out the video and practice problems below for even more. Happy calculating! 🙂

Looking to review different types of sequences? Check out this post here!

## What does it mean to find the “Sum of Infinite Geometric Sequence” (Series)?

We already know what a geometric sequence is: a sequence of numbers that forms a pattern when the same number is multiplied or divided to each term.

Example:

But when what happens if we wanted to sum all the terms of our geometric sequence together?

Example:

We can also write our infinite geometric series using Summation Notation:

How would we calculate that?  That’s where our Infinite Geometric Series formula will come in handy! But before we find a solution, lets take a closer look at what geometric series qualify for this formula.

## Divergence Vs. Convergence:

There are two types of Infinite Geometric Series:

Type 1: Infinite Geometric Series that diverges to infinity

Type 2: Infinite Geometric Series that converges to a numeric value (-1 < r < 1)

Check out the differences in the example below:

## Infinite Geometric Series Formula:

Note that the below infinite geometric series formula can only be used if the common ratio, r, is less than 1 and greater than -1. If the common ratio, r, is not between -1 and 1, then the sum of the geometric sequence diverges to infinity (and the formula cannot be used).

Now that we have a formula to work with and know when to use it (when -1 < r < 1), let’s take another look at our question and apply our infinite geometric series formula to find a solution:

Step 1: First, let’s identify the common ratio to make sure that its between -1 and 1.

Step 2: Now that we know we can use our formula, let’s write out each part and identify what numbers we are going to plug in.

Step 3: Now let’s fill in our formula and solve with the given values.

## Practice Questions:

State if each series converges or diverges, then if applicable find the solution.

## Solutions:

Still got questions? No problem! Don’t hesitate to comment with any questions or check out the video above. Happy calculating! 🙂

*Also, if you want to check out Finite Geometric Series click this link here! And if you want to learn about even more sequences, check out the link here!

## Mobius Bands￼

Greeting math friends and welcome to another fabulous week of MathSux! Today we are going to look at how to make a Mobius Strip otherwise known as “mobius bands.” Whatever you call them, they are a one of a kind shape that leads to all sorts of questions and math exploration. So let’s get to it! Let’s start off by explaining what a mobius strip is:

## What are Mobius Bands?

A mobius strip (or band) is a two-dimensional shape that only has one surface.  Invented by German mathematician August Ferdinand Mobius and also independently by Johann Benedict Listing in the 1800s, it is considered a mathematical phenomenon! We are going to create our own mobius strip today to understand why this shape is so fascinating!

*Note: You may also see different spelling of the mobius band: including Möbius or Moebius

## How to Make a Mobius Strip:

Step 1: First, let’s gather out materials. For this activity we will need a piece of paper, scissors, tape, and a pencil.

Step 2: Let’s cut out a rectangle. The size of the one shown above is 11 X 1 inches. Once you have your rectangle, take one end of the rectangle and give it a half twist.

Step 3: Now take the half twisted piece and attach it to the other end of the rectangle with a piece of tape. Behold the beauty of our mobius strip!

Step 4: Now we are going to take a pen or pencil and draw a line going all around the mobius strip without lifting the pen. See if you can move he mobius strip along, while the pencil remains where it is.  Notice anything special happen? We created a line around the entire shape without lifting our pencil!

## Real-World Mobius:

Have you been pondering where we can find Mobius bands in the real world? I thought so! Take a look at the list below:

• Printer ink cartridges
• Serpentine Belt in a car
• VHS tapes (if anyone remembers or knows what those are)
• Can you think of anymore? Let me know in the comments below!

## Worksheet:

I also made this FREE worksheet to go along with the above video and lesson for anyone interested. Let me know if this is helpful! 🙂

If you’re looking for more fun math projects, check out my “Just for Fun” page here. And if you want to get to see the latest MathSux content, don’t forget to follow along with us and subscribe via the links below. Thanks so much for stopping by and happy calculating! 🙂

## Math Jewelry Review: Hanusa Design

Hi Everyone and welcome to MathSux! I was sent three pieces of math jewelry from the jewelry brand, Hanusa Design. Math jewelry?! What is that?! Each piece you see here was inspired by mathematical art and created using 3D printing. I’m wearing the mobius necklace above and below you’ll also see mini pi and golden ratio earrings. For the full un-boxing and math jewelry review check out the video below and if you’re interested and want to learn more about Hanusa designs and the 3-d printing process, keep reading for the full interview I had with founder, Chirs Hanusa himself in this blog post.

## Math Jewelry Review:

1.What made you start Hanusa Design? What led you to making jewelry as someone interested in math?

My adventure into 3D printing started in 2015 when I was updating a course in Mathematica I was teaching at Queens College. I was intrigued by 3D printing and I noticed that it was possible to use Mathematica as 3D design software, so I included a 3D design project as part of the class. As my students and I explored 3D printing, I recognized the universal appeal of the beauty and precision of mathematical concepts, and turned these ideas into jewelry. In turn, I founded Hanusa Design in 2017.

2. The jewelry is made through a 3D printing process. Can you explain the process from start to end? Is there a difference between the use of metal vs. nylon?

The design process starts with a mathematical concept that I’ve seen in my research, in mathematical texts, or as “found math” in the real world. I use Mathematica to do the 3D design, using three-dimensional coordinates, parametric functions, and aesthetic choices that turn the idea into a 3D model. The model is then exported directly from Mathematica to an STL file, which is basically a way to represent the boundary of the 3D object as a collection of triangles. The STL files are then sent to a 3D printer.

Once there, the same STL file can be used to create a nylon or metal piece of jewelry. The colorful nylon pieces are created using a SLS (selective laser sintering) process, where a thin layer of nylon powder is spread out and precisely fused to the previous layer using a laser. The excess powder is removed and then I hand dye the models using fabric dye. In contrast, the metal pieces are created using a lost-wax casting process. First, the models are 3D printed in high-resolution wax, then a plaster mold is created around the wax, and then the wax is replaced by molten metal.

3.I saw on your website that you are a mathematician and mathematical artist. Do you teach mathematical art at a university? If so, what types of topics do you cover? What is your favorite form of mathematical art?

I do teach two different courses that involve mathematical art. I teach a class called Mathematical Design that explores art that is created with functions, parametric functions, and polar functions using Desmos. This year I hope to give my Mathematical Design students the opportunity to use the Queens College Makerspace to take their digital art and bring it into reality using a laser cutter, a sewing machine, or a pen plotter. My other class is called Mathematical Computing. In this class I teach my students the computational software Mathematica, including how to use the software to do 3D modeling.  By the end of the semester, the students have designed and 3D printed a mathematical sculpture.

I suppose my favorite type of mathematical art is the visualization of complex mathematical concepts. It’s hard to understand certain concepts, like constructions in the fourth (or higher) dimension. Any picture or sculpture that helps clarify these difficult ideas is important, and it’s even better when it’s created with an eye to the aesthetic. I highly recommend any work by Henry Segerman.

4.I saw on your website that Hanusa Design has been featured in both New York Fashion Week (NYFW) and MoMath.  In what capacity?  Are you being featured in this week’s NYFW Fall 2021?

A wide variety of Hanusa Design jewelry has been available in the gift shop at the National Museum of Mathematics since 2018, including my dangling cubes earrings and interlocking octahedron necklace. I was asked to participate in a New York Fashion Week-adjacent show in Spring 2019 and enjoyed the experience. I am looking forward to eventually participate in New York City Jewelry Week.

5.Where can we find Hanusa Design, in stores or online?

A variety of museums, galleries, and stores stock Hanusa Design Jewelry. As I mentioned before, it is available at the National Museum of Mathematics in New York, NY. It can also be found at the Exploratorium in San Francisco, CA, the Queens Museum in Queens, NY, Gallery North in Setauket, NY, Because Science in Vienna, VA, and in the Wolfram Store in Champaign, IL.

## Hanusa Design Discount:

Hanusa has been kind enough to give MathSux readers an exclusive 10% off discount with the code ‘MATHROCKS’ now through December 31st 2021. I know its a bit early but this would be the perfect gift for the holiday season which is coming around the corner! Check out the full collection on their website here for even more designs and colors!

## MathSux Giveaway:

I’m going to be giving away a pair of pi earrings to one lucky MathSux reader! All you have to do is watch the YouTube video above, subscribe to MathSux, and comment below.

What do you guys think of Hanusa Design? Would you wear mathematical jewelry? What about the 3D printing process? Don’t forget to check out the video above for the full math jewelry review. Let me know what you guys think and happy calculating! 🙂

If you’re looking for more mathematical reviews, check out my review on the NumWorks calculator here.

## Angle Bisector Definition & Example

Hi everyone and welcome to another fabulous week of MathSux! I bring to you the first construction of the back to school season! In this post, we are going to go over the angle bisector definition and example. First, we will define what an angle bisector is, then we’ll take our handy dandy compass and straight edge to construct an angle bisector that will bisect an angle for any size! Check out the video and GIF below for more and happy calculating! 🙂

## What is an Angle Bisector?

A line that evenly cuts an angle into two equal halves, creating two equal angles.

## Angle Bisector Example:

Step 1: Place the point of your compass on the point of the angle.

Step 2: Draw an arc that intersects both lines that stem form the angle you want to bisect.

Step 3: Take the point of your compass to where the lines and arc intersect, then draw an arc towards the center of the angle.

Step 4: Now keeping the same distance on your compass, take the point of your compass and place it on the other point where both the line and arc intersect, and draw another arc towards the center of the angle.

Step 5: Notice we made an intersection!? Where these two arcs intersect, mark a point and using a straight edge, connect it to the center of the original angle.

Step 6: We have officially bisected our angle into two equal 35º halves.

*Please note that the above example bisects a 70º angle, but this construction method will work for an angle of any size!🙂

What do you think of the above angle bisector definition & example? Do you use a different method for construction? Let me know in the comments below! 🙂

## Best Geometry Tools!

Looking to get the best construction tools? Any compass and straight-edge will do the trick, but personally, I prefer to use my favorite mini math toolbox from Staedler. Stadler has a geometry math set that comes with a mini ruler, compass, protractor, and eraser in a nice travel-sized pack that is perfect for students on the go and for keeping everything organized….did I mention it’s only \$7.99 on Amazon?! This is the same set I use for every construction video in this post. Check out the link below and let me know what you think!

Looking for more constructions? Check out how to construct a square inscribed in a circle and an equilateral triangle by clicking on their respective links! And if you’re looking for even more geometry constructions, check out the link here!

AnAngle Bisector Definition & Example

## How to Find Expected Value

Greeting math friends! Today, we are going to dive into statistics by learning how to find the expected value of a discrete random variable. To do this we will need to know all potential numeric outcomes of a “gamble,” as well as be able to repeat the gamble as many time as we want under the same conditions, without knowing what the outcome will be. But I’m getting ahead of myself, all of this will be explained below with two different examples step by step! Don’t forget to check out the video and practice questions at the end of this post to check your understanding. Happy calculating! 🙂

## What is Expected Value?

Expected Value is the weighted average of all possible outcomes of one “game” or “gamble” based on the respective probabilities of each potential outcome.

Expected Value Formula: Don’t freak out because below is the expected value formula.

In essence, we are multiplying each outcome value by the probability of the outcome occurring, and then adding all possibilities together!  Since we are summing all outcome values times their own probabilities, we can re-write the formula in summation notation:

Does the above formula look insane to you?  Don’t worry because we will go over two examples below that will hopefully clear things up! Let check them out:

## Example #1: Expected Value of Flipping a Coin

Step 1:  First let’s write out all the possible outcomes and related probabilities for flipping a fair coin and playing this game.  Making the below table, maps out our Probability Distribution of playing this game.

Step 2: Now that, we have written out all numeric outcomes and the probability of each occurring, we can fill in our formula and find the Expected Value of playing this game:

Ready for another?  Let’s see what happens in the next example when rolling a die.

## Example #2: Expected Value of Rolling a Die

Step 1:  First let’s write out all the possible outcomes and related probabilities for rolling a die. In this question, we are assuming that each side of the die takes on its numerical value, meaning rolling a 5 or a 6 is worth more than rolling a 1 or 2.  Making the below table, maps out our Probability Distribution of rolling the die.

Step 2: Now that, we have written out all numeric outcomes and the probability of each occurring, we can fill in our formula and find the Expected Value of playing this game:

Check out the practice problems below to master your expected value skills!

## Practice Questions:

(1) An unfair coin where the probability of getting heads is .4 and the probability of getting tails is .6 is flipped.  In a game where you win \$10 on heads, and lose \$10 on tails, what is the expected value of playing this game?

(2) An unfair coin where the probability of getting heads is .4 and the probability of getting tails is .6 is flipped.  In a game where you win \$30 on heads, and lose \$50 on tails, what is the expected value of playing this game?

## Solutions:

Still got questions? No problem! Don’t hesitate to comment with any questions below. Thanks for stopping by and happy calculating! 🙂

Looking for something similar to Expected Value? Check out the statistics page here!

## How to Solve for Exponents

Greetings math peeps! In today’s post, we are going to look at how to solve for exponents. At this point, we are familiar with solving for unknown variables within an equation, but never before did we have to solve for an exponent! Understanding how to do this and what method(s) to use will take our algebra skills to a whole new level. Also, don’t forget to check out the video and practice questions in this post for even more examples. Happy calculating! 🙂

## What is an Exponential Equation?

An exponential equation, is an equation where the exponent is an unknown variable and takes the following form:

Sometimes we will be asked to solve for the unknown variable in an exponential equation. There are two main ways of solving for this type of equation and we’ll go over each type below.

(Method 1) Same Base

(Method 2) Different Base

Let’s dive right in and look at three different examples applying one of the two methods above.

## Example #1: Solving Exponential Equations with the Same Base

Whenever an equation has the same base, like in the example below (both bases are 5), we can set the exponents equal and solve for the missing variable.

Step 1: Since both sides of the equation have the same base (a base of 5), we can set the exponent values equal to each other and use basic algebra to solve for x.

## Example #2: Solving Exponential Equations with the Same Base

We can set exponents equal to each other whenever an equation can be written to have the same base on either side. Like in the example below both bases can be written as 5, we can again, set the exponents equal and solve for the missing variable.

Step 1: Re-write the right part of the equation so the bases on either side match.  In this case we need to re-write 25 as 5^2. Make sure to keep the part of the exponent, 2x, that was already attached to the 25 so it becomes, 5^2(2x).

Step 2: Now we can set the exponent values equal to each other and solve for x now that both sides have matching bases.

## Example #3: Solving Exponential Equations with the Different Bases

When an exponential equation doesn’t have the same base and cannot be written to have the same base, we must use logs to solve for the unknown variable!  So, make sure you are comfortable with the log rules listed here in order to solve these types of questions. We are mainly going to be working with the power rule of logs.

Step 1: Take log of both sides and solve for x.

When you’re ready check out the practice questions below to own your new exponent skills!

## Practice Questions:

Solve each exponential equation for x.

## Solutions:

Looking to review logs? Check out this post here!

## How to Tell if Something is a Function?

Greetings math peeps and welcome to MathSux! In todays post we will be exploring how to tell something is a function or not. We’ll start off by defining what a function is, go over its notation, and then look at several different examples of how to recognize a function in different formats including function maps, tables, and graphs! Functions are a concept that is seen throughout algebra and mathematics so understanding it well is key to learning more! Also, don’t forget to check out the video and practice problems at the end of this post to practice your skills! Happy calculating! 🙂

## What is a Function?

A function works like a machine with inputs and outputs. When we input a number into a function, a new number pops right back out. We can say that a function is like a machine because it transforms one number into a completely different number once it enters this so called “machine.”

Let’s look at an example in action, where f(x)=2x+1 is the function and we want to see what happens when we plug inout a 3 into our function.

Notice we plugged in 3 into the variable x and solved, to get the output 7.

## Function Notation:

Functions have their own notation, when we have f(x)=2x+1, this can also be written as g(x), h(x), or any other letter you can think of!

In the previous input/output example, the input value 3 is plugged into the function f(x)=2x+1 for the missing variable, x to get the output 7.

Another way to write what we did in function notation is to say that we found the value for f(3)=6 for the function f(x).

## How to Tell if Something is a Function?

A main and important rule of functions is that there is always one unique input, but there can be different or repeating outputs. Let’s look at some examples below, at how to identify a function.

Example #1:Function Maps

Example #2: Tables

Example #3: Graphs

In order to know if a function is a function when looking at graph, we perform something called a Vertical Line Test. All we must do is draw a vertical line, if the line hits the graph one time, the graph is a function! If the vertical line his more than that, the graph is not a function.

Try the following practice questions to test your skills below!

## Practice Questions:

Identify if the following are functions or not and explain your reasoning.

## Solutions:

Looking to learn more about Algebra? Check out the algebra lessons page here. Thanks for stopping by and happy calculating! 🙂

## Why “MathSux”?

Hi Everyone and welcome to MathSux! Today, I wanted to answer a question I get a lot which is why name your Blog and YouTube channel, “MathSux”? Clearly, I love math, but with the name “MathSux” I wanted to show that it can also be hard and even I can think that it suck sometimes. When we don’t understand something it can be frustrating whether its related to math or really anything! The point is we’ve all gotten frustrated when learning something new at some time, but that’s ok, and that’s exactly what MathSux stands for! 🙂

Check out the video below to hear why I chose the name “MathSux” while doodling math art . I hope you enjoy it and happy calculating! 🙂

## Why is it called “MathSux”?

*New lessons will be coming your way starting next Wednesday. Also be on the lookout for Regents review questions up on YouTube tomorrow and Friday! 🙂

If you are a teacher or student, have you ever thought math sucked at some time in your life? Let me know in the comments below!

And for more “Just for Fun” math posts and videos, click the link here.

## Back to School Review

Hey math friends and welcome back to MathSux! Back to school season is upon us which means most students (and teachers) will need to review a bit before diving into a completely new subject.  In order to alleviate some of the back to school whoas, I bring to you, this back to school review! Check out the videos below to get the math juices flowing whether you’re new to Algebra, Geometry, or Algebra 2/Trig! I hope you find these videos helpful and wish everyone the best of luck in their first days at school! Happy calculating! 🙂

## How to Prepare for Algebra:

Calling all incoming algebra students, Combining Like Terms is a great place to start! You most likely have combined like terms before, but there’s nothing like sharpening your skills before getting the intense Algebra questions that are coming your way. Check out the video below and try the practice questions here!

## How to Prepare for Geometry:

Geometry students, you have the world of shapes ahead of you! It’s an exciting time to review basic Area, Perimeter, Circumference, and Pythagorean Theorem rules before moving ahead with this subject. Review the Pythagorean Theorem below from Khan Academy and check out the last page of the review sheet here to review area and perimeter.

## How to Prepare for Algebra 2:

Relieve the fond memories of algebra by reviewing all the different ways to Factor and Solve Quadratic Equations! This is a great way to prepare for rational expressions and the harder algebra 2 problems that are right around the corner.  Check out the video below and related practice questions here to reinforce these hopefully not yet forgotten algebra skills!

Hope you find this quick review helpful before diving in for the real deal! Besides brushing up on these math topics, what type of new school year routines do like to practice in your classroom or at home? Let me know in the comments and happy calculating! 🙂

## Olympics Statistics: Top 10 Medals by Country

Greetings and welcome back to MathSux! This week, in honor of the Tokyo Olympics, I will be breaking down some Olympic Statistics. We will look at the top 10 countries that hold the most medals and then look at the top 10 medals earned by country in relation to each country’s total population. Let’s take a look and see what we find! Also, please note that all data used for this analysis was found on the website, here. Anyone else watching the Olympics? Try downloading the data with the link above and see what type of conclusions you can find! Happy Calculating! 🙂