You know about ebooks, but have you heard of dbook?

Two years ago, I attended a lecture of Professor Masami Isoda about dbook, a flash-based software developed by CRICED at the University of Tsukuba in Japan used for creating interactive digital textbooks.  The usual practice in dbook is taking a picture (or scanning) of book pages and embedding ready-made tools to construct an interactive worksheets.

The mathematics electronic whiteboard that I have posted here was an empty file of dbook. If you want to know more about dbook, and download the software, click here.

I will make a tutorial about dbook soon, so keep posted.

Demystifying Degree and Radian Measures

Introduction

We have learned about angle measures since elementary grades.  In Figure 1, we have a circle with center A, and radius length 1. Angle CAB measures 90 degrees and intercepting minor arc BC.  This is also the same as saying that arc BC is subtending angle CAB. We have also learned  that the entire rotation about the center of a circle is 360 degrees.

Another unit of angle measure besides degree is radian. Now, what is radian? How is it related to degree? » Read more

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