Understanding the Meaning of Absolute Value

One important concept in algebra that we learn is the distance between two points on the number line. In particular, we study the distance of a point that corresponds to a number to the point that corresponds to 0. In the following figure, the point (or circle) on the left represents 0, while the point on the right represents 5. To simplify our language, we will use coordinates to refer to its corresponding point on the number line. For instance, we will use -8 to refer to the point that corresponds to -8.

Looking at the number line, it is easy to see that 5 is 5 units away from 0 and that -8 is 8 units away from 0. We can also see that 0 is 0 units away from 0. The distance of a number from 0 on the number line is called its absolute value. Hence, the absolute value of 5 is equal to 5, the absolute value of -8 is equal to 8, and the absolute value of 0 is equal to 0. » Read more

Sync Your Cloud Storage and Your Phone with FolderSync

I started using an Android phone three months ago and since then, I have been searching for some apps that would fit my needs as a teacher. One of the apps that I have been using which was really useful to me is Foldersync. It enables you to sync your cloud storage with your local mobile phone storage. You can also use it with your phone’s SD card.

What I like most about Foldersync is it enables you to sync a specific folder and not your entire cloud storage with your phone. In my case, I only have a 64GB storage, so I did not want sync my entire Dropbox to my phone because it will take up a lot of space. I use a specific folder to sync my electronic books folder on my Dropbox and my phone.

Foldersync

Foldersync at Google Play Store

Foldersync supports the following locally and on the cloud: updating of files, copying, moving, and deleting files, and creating files and folders. Although I have not tried it yet with other cloud storage,  it works perfectly in my experience with Dropbox. It has a free version (the Foldersync Lite) which contains ads and it also has a premium version. I’ve been using the free version for three months already and I am perfectly satisfied with it.

Foldersync is also compatible with Google Drive, Amazon S3, Godaddy, Amazon S3, OneDrive, OneDrive for Business and many others (see full description on Playstore). It is available for Android users and can be downloaded from the Google Playstore.  There is also a very detailed setup guide at the How To Geek website.

The Dancing Triangle and Its Applications

In the figure below, lines l and m are parallel lines. What can you say about the areas of triangle ABC and triangle ADC?

The distance between two parallel lines is equal at any point, so the two triangles have the same altitude (can you see why?). Further, the two triangles have a common base, therefore, their base lengths are equal. So, the areas of the two triangles are equal. In fact, you can choose any point P on line l and the areas of the triangle ACP will always equal to the areas of triangles ABC and ADC. We like to call this triangle the dancing triangle because using an applet, you can dance it by moving P without changing the area. In the applet below, move points B and D to dance the triangle.  » Read more

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