Wolfram Algebra Course, by Wolfram Alpha L.L.C., is $1.99. Titles for calculus, music theory, and other subjects are also available at various prices for Android and Apple. The algebra course provides opportunities to view examples or to plug in an equation to examine its parts, calculate a solution, plot the results, and . . . do more math stuff than I was ready for.
The Wolfram courses are an extension of the brilliant "computational knowledge engine" at Wolframalpha.com, which handles a lot of the inquiries that iPhone4s users put to the "personal assistant" app, Siri.
HowStuffWorks, by HowStuffWorks.com, is a free, advertising-supported app version of the popular website, for Apple and Android. It has a search screen, podcasts such as "Stuff You Missed in History Class" and "Car Stuff," and chat and tweet functions. Share or save your findings.
Homeworkhelp.com makes dozens of subject-specific apps for learning and review. They include instruction for SAT and ACT preparation. Titles in the App Store, some free, some not, include lessons in various levels of math, the state capitals, grammar, and vocabulary.
I looked at Homeworkhelp.com's $2.99 Probability and Statistics app. Lessons begin simply by explaining the practical uses for knowing probability, and progress through frequency tables, exponential distributions, and linear regression. Some reviewers complain about there being no practice problems.
Encyclopaedia Britannica is $1.99 a month for iPhone. I grew up in a house with a sagging bookshelf of encyclopedia volumes, including the massive Britannica. It's still authoritative, but now it fits in your pocket, has more features, and costs way less.
In an article, tap the "link map" icon to see a chart of related topics and articles for easy browsing. You can turn off your subscription renewals in iPhone settings.
Contact staff writer Reid Kanaley at rkanaley@phillynews.com, 215-854-5114 or @ReidKan on Twitter.
