Computable Document Format

I've recently become aware of Wolfram's Computable Document Format or CDF as it's referred to. It adds interactivity to documents in a manner similar to Apple's iBooks Author, that allows anyone to create interactive textbooks for reading in iBooks. You need to download the CDF player, which I've done, but it's a hefty 2.2 GB in size. With the player installed you can then open CDF files. The format is clearly proprietary and it remains to be seen how much traction it will get in the marketplace.

Here is what Wikipedia has to say about CDF:

Features 

Computable document format supports GUI elements such as sliders, menus and buttons. Content is updated using embedded computation in response to GUI interaction. Contents can include formatted text, tables, images, sounds and animations. CDF supports Mathematica typesetting and technical notation. Paginated layout, structured drill down layout and slide-show mode are supported. Styles can be controlled using a cascading style sheet. 

Reading 

CDF files can be read using a proprietary CDF Player with a restrictive license, which can be downloaded free of charge from Wolfram Research. 

Authoring 

CDF Files can be created using Mathematica. Online authoring tools are planned. 

Uses 

Computable Document Format has been used in electronic books by Pearson Education, to provide the content for the Wolfram Demonstrations Project, and to add client-side interactivity to Wolfram Alpha.

Now that I'm aware of the product I can monitor its fortunes. 

Symbolab

I've just had a look at a website called Symbolab that offers a many tools for the mathematics student and even the chemistry student. I tested it out with the following rather difficult integral:

I was impressed with the step-by-step solution provided for the problem. It was quite thorough. It seems to be largely free, although there is a modestly priced paid option, and there is both an Android and iOS app that I'll download and test out. It seems a worthy competitor to WolframAlpha that doesn't offer free, step-by-step solutions on its website or apps.

I was made aware of the site thanks to Richard Byrne's tweet:

https://twitter.com/rmbyrne/status/775696157171253248

I used to follow this guy but hadn't been doing so over the past year since I retired from full-time teaching. However, I reconnected yesterday and the reconnection is already paying benefits. I've opened a free account using my Facebook login.

UPDATE: having now downloaded the Android app, I've found that the step-by-step solutions are only available with a one-off payment of $9.99 (US dollars presumably) which is a lot more than WolframAlpha is asking. The iOS app is the same except that it wants $10.99. Consequently, I've uninstalled both the Android and iOS apps and will simply use the desktop version while it still provides the steps for free. The web version is still limited in various ways. For example, the full range of practice questions on various topics is only available via a subscription. 

WolframAlpha

For the PRO version of the desktop WolframAlpha, there is a charge $6.99 per month (on a month by month basis) and I'm not sure whether the quote is for United States or Australian dollars. However, the mobile version of WolframAlpha seems to offer some, perhaps all, of the features of the desktop PRO version for a one-off cost of A$4.99. Whether it's totally equivalent to the PRO version or not I'm not sure but it certainly provides the step-by-step solutions that the former offers.

Anyway, I've made the mobile purchase and am experimenting with it. I tried the step-by-step solution to integrating ln(x^2+1) and it's displayed in the mobile app but I can't see how to copy it. Screenshots can of course be taken and this is what I've done below. The result is OK I guess.

Reconnecting

I just looked at my previous post, made over a year ago now. I'd forgotten all about my integer equations based on the number of days I'd been alive. Today is day number 23924 and sure enough: $$(2-3) = -9 +(2 \times 4)$$For most of the previous year, I kept a daily blog going at voodooguru.postach.io generated from within a notebook in Evernote. Most the information for each day's number was taken from either WolframAlpha or the Online Encyclopedia of Integer Sequences. During my break in Jakarta I stopped completely; however, I've now resumed but am only tracking my prime days. I needed a break. My next prime day is Wednesday October 8th when I'll be 23929 days old.

23934 by the way is equal to 2 x 2 x 5981 so today my life can be divided exactly into four equal parts each of about 16.375 years duration. So the sequence is 16.375, 32.75, 49.125 and 62.5 (minus a day for each quarter because I'm about four days away from the 62.5 milestone). So sometime in May 1998 I was exactly 75% of my current age.